Alkali enrichment mediated co2 sequestration methods, and systems for practicing the same

ABSTRACT

Methods of sequestering CO 2  from a gaseous source of CO 2  are provided. Aspects of the methods include employing an alkali enrichment protocol, such as a membrane mediated alkali enrichment protocol, in a CO 2  sequestration protocol. Also provided are systems for practicing the methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims priority to thefiling dates of U.S. Provisional Application Ser. No. 61/947,372 filedon Mar. 3, 2014; U.S. Provisional Application Ser. No. 62/041,568 filedon Aug. 25, 2014; U.S. Patent Application Ser. No. 62/051,100 filed onSep. 16, 2014; U.S. Patent Application Ser. No. 61/990,486 filed on May8, 2014; U.S. Provisional Application Ser. No. 62/056,377 filed on Sep.26, 2014; U.S. Application Ser. No. 62/062,084 filed on Oct. 9, 2014;and U.S. Provisional Application Ser. No. 62/096,340 filed on Dec. 23,2014; the disclosures of which applications are herein incorporated byreference.

INTRODUCTION

Carbon dioxide (CO₂) is a naturally occurring chemical compound that ispresent in Earth's atmosphere as a gas. Sources of atmospheric CO₂ arevaried, and include humans and other living organisms that produce CO₂in the process of respiration, as well as other naturally occurringsources, such as volcanoes, hot springs, and geysers.

Additional major sources of atmospheric CO₂ include industrial plants.Many types of industrial plants (including cement plants, refineries,steel mills and power plants) combust various carbon-based fuels, suchas fossil fuels and syngases. Fossil fuels that are employed includecoal, natural gas, oil, petroleum coke and biofuels. Fuels are alsoderived from tar sands, oil shale, coal liquids, and coal gasificationand biofuels that are made via syngas.

The environmental effects of CO₂ are of significant interest. CO₂ iscommonly viewed as a greenhouse gas. Because human activities since theindustrial revolution have rapidly increased concentrations ofatmospheric CO₂, anthropogenic CO₂ has been implicated in global warmingand climate change, as well as ocean acidification.

Sequestration of anthropogenic CO₂ is of great global urgency and isimportant in efforts to slow or reverse global warming and oceanacidification.

SUMMARY

Methods of sequestering CO₂ from a gaseous source of CO₂ are provided.Aspects of the methods include employing an alkali enrichment protocol,such as a membrane mediated alkali enrichment protocol, in a CO₂sequestration protocol. Also provided are systems for practicing themethods.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a membrane mediated alkali enrichment protocol.

FIG. 2 illustrates an osmotic pressure mediated alkali enrichmentprotocol.

FIG. 3 illustrates an ionic concentration mediated alkali enrichmentprotocol.

FIG. 4 A monovalent cation selective membrane can convert an initialsodium chloride solution (left) in proximity with a low salinitysolution (right) to a HCl solution in proximity with a NaOH solution,respectively. This is done by allowing, sodium and hydrogen ions (H+) topass freely through the membrane at a cost of 18.5 kcal/mol. The drivingforce which fuels the non-spontaneous reaction is osmotic pressure dueto the high salinity of the initial NaCl solution (left) compared to thelow salinity of the fresh water solution (right). The sodium hydroxidesolution can be used at a later stage to sequester carbon dioxide.

FIG. 5 A monovalent cation selective membrane can convert an initialsodium chloride solution (left) in proximity with a low salinity CO₂(aq)-containing solution (right) to a HCl solution in proximity with aNaHCO3 solution, respectively. This is done by allowing, sodium andhydrogen ions (H+) to pass freely through the membrane at a cost of 7kcal/mol (based on Gibbs free energy of Formation). The driving forcewhich fuels the non-spontaneous reaction is osmotic pressure due to thehigh salinity of the initial NaCl solution (left) compared to the lowsalinity of the fresh water solution (right). The process results in aconversion of CO₂ (aq) to bicarbonate ion, which can be used toprecipitate minerals at a later point.

FIG. 6 A monovalent cation selective membrane can convert an initialsodium chloride solution (left) in proximity with a relatively lowersalinity NaHCO₃ (solution (right) to a HCl solution in proximity with aNaHCO₃ solution, respectively. This is done by allowing, sodium andhydrogen ions (H+) to pass freely through the membrane at a cost of 11.5kcal/mol (based on Gibbs free energy of formation). The driving forcewhich fuels the non-spontaneous reaction is osmotic pressure due to thehigh salinity of the initial NaCl solution (left) compared to the lowsalinity of the initial sodium bicarbonate solution (right). The processresults in a conversion of bicarbonate to carbonate and creates a highpH, high alkalinity solution which can be used for CO₂ sequestration ata later point.

FIG. 7 illustrates a specific cation ion exchange membrane (i.e.,cationic membrane) mediated alkali enrichment protocol.

FIGS. 8 and 9 illustrate anionic ion exchange membrane (i.e., anionicmembrane) mediated alkali enrichment protocols.

FIG. 10 provides an illustration of a composite metal particle membranein accordance with an embodiment of the invention.

FIGS. 11 to 27 illustrate embodiments of specific alkali enrichmentprotocol mediated CO₂ sequestration processes.

FIG. 28 Alkali enrichment may be used to capture and sequester carbondioxide by using generated alkalinity to convert carbon dioxide tocarbonate and bicarbonate ions. The schematic demonstrates a particularcase where one might want to conduct this process in multiple smallsteps (3 shown above but more steps may be desirable). This may beadvantageous if efficiency is a larger concern than capital costs.

DETAILED DESCRIPTION

Methods of sequestering CO₂ from a gaseous source of CO₂ are provided.Aspects of the methods include employing an alkali enrichment protocol,such as a membrane mediated alkali enrichment protocol, in a CO₂sequestration protocol. Also provided are systems for practicing themethods.

Before the present invention is described in greater detail, it is to beunderstood that this invention is not limited to particular embodimentsdescribed, as such may, of course, vary. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only, and is not intended to be limiting, sincethe scope of the present invention will be limited only by the appendedclaims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges and are also encompassed within the invention, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention.

Certain ranges are presented herein with numerical values being precededby the term “about.” The term “about” is used herein to provide literalsupport for the exact number that it precedes, as well as a number thatis near to or approximately the number that the term precedes. Indetermining whether a number is near to or approximately a specificallyrecited number, the near or approximating un-recited number may be anumber which, in the context in which it is presented, provides thesubstantial equivalent of the specifically recited number.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present invention, representativeillustrative methods and materials are now described.

All publications and patents cited in this specification are hereinincorporated by reference as if each individual publication or patentwere specifically and individually indicated to be incorporated byreference and are incorporated herein by reference to disclose anddescribe the methods and/or materials in connection with which thepublications are cited. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that the present invention is not entitled to antedate suchpublication by virtue of prior invention. Further, the dates ofpublication provided may be different from the actual publication dateswhich may need to be independently confirmed.

It is noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. It is further noted that the claimsmay be drafted to exclude any optional element. As such, this statementis intended to serve as antecedent basis for use of such exclusiveterminology as “solely,” “only” and the like in connection with therecitation of claim elements, or use of a “negative” limitation.

As will be apparent to those of skill in the art upon reading thisdisclosure, each of the individual embodiments described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentinvention. Any recited method can be carried out in the order of eventsrecited or in any other order which is logically possible.

In further describing various aspects of the invention, methods will bereviewed first in greater detail, followed by a review of systems.

Alkali Enrichment Mediated Co₂ Sequestration Methods

As summarized above, aspects of the invention include methods ofsequestering CO₂, i.e., CO₂ sequestration processes (i.e., methods,protocols, etc.) that result in CO₂ sequestration. By “CO₂sequestration” is meant the removal or segregation of an amount of CO₂from an environment, such as the Earth's atmosphere or a gaseous wastestream produced by an industrial plant, so that some or all of the CO₂is no longer present in the environment from which it has been removed.CO₂ sequestering methods of the invention sequester CO₂ in a number ofdifferent ways, e.g., by producing a CO₂ sequestering product, e.g. acarbonate material, and/or by producing a substantially pure subsurfaceinjectable CO₂ product gas from an amount of initial CO₂, such that theCO₂ is sequestered. The CO₂ sequestering product may be a storage stablecomposition that incorporates an amount of CO₂ into a storage stableform, such as an above-ground storage or underwater storage stable form,so that the CO₂ is no longer present as, or available to be, a gas inthe atmosphere. Sequestering of CO₂ according to methods of theinvention results in prevention of CO₂ gas from entering the atmosphereand allows for long-term storage of CO₂ in a manner such that CO₂ doesnot become part of the atmosphere.

Alkali Enrichment Protocol

As summarized above, CO₂ sequestration methods of the invention arealkali enrichment protocol mediated methods. By alkali enrichmentprotocol mediated methods is meant that the methods employ an alkalienrichment protocol at some point during the method, e.g., to produce aCO₂ capture liquid, to enhance the alkalinity of a CO₂ charged liquid,etc. The alkali enrichment protocol may be employed once or two or moretimes during a given method, and at different stages of a given method.For example, an alkali enrichment protocol may be performed beforeand/or after a CO₂ capture liquid production step, e.g., as described ingreater detail below.

By “alkali enrichment protocol” is meant a method or process ofincreasing the alkalinity of a liquid. The alkalinity increase of agiven liquid may be manifested in a variety of different ways. In someinstances, increasing the alkalinity of a liquid is manifested as anincrease the pH of the liquid. For example, a liquid may be processed toremove hydrogen ions from the liquid to increase the alkalinity of theliquid. In such instances, the pH of the liquid may be increased by adesirable value, such as 0.10 or more, 0.20 or more, 0.25 or more, 0.50or more, 0.75 or more, 1.0 or more, 2.0 or more, etc. In some instances,the magnitude of the increase in pH may vary, ranging in some instancesfrom 0.1 to 10, such as 1 to 9, including 2.5 to 7.5, e.g., 3 to 7. Assuch, methods may increase the alkalinity of an initial liquid toproduce a product liquid having a desired pH, where in some instancesthe pH of the product liquid ranges from 5 to 14, such as 6 to 13,including 7 to 12, e.g., 8 to 11, where the product liquid may be viewedas an enhanced alkalinity liquid. The increase in alkalinity of a liquidmay also be manifested as an increase in the dissolved inorganic carbon(DIC) content of liquid. The DIC is the sum of the concentrations ofinorganic carbon species in a solution, represented by the equation:DIC=[CO₂*]+[HCO₃ ⁻]+[CO₃ ²⁻], where [CO₂*] is the sum of carbon dioxide([CO₂]) and carbonic acid ([H₂CO₃]) concentrations, [HCO₃ ⁻] is thebicarbonate concentration and [CO₃ ²⁻] is the carbonate concentration inthe solution. The DIC of the alkali enriched liquid may vary, and insome instances may be 500 ppm or greater, such as 5,000 ppm or greater,including 15,000 ppm or greater. In some instances, the DIC of thealkali enriched liquid may range from 500 to 20,000 ppm, such as 7,500to 15,000 ppm, including 8,000 to 12,000 ppm. In some instances, alkalienrichment is manifested as an increase in the concentration ofbicarbonate species, e.g., NaHCO₃, e.g., to a concentration ranging from5 to 500 mMolar, such as 10 to 200 mMolar.

In some instances, the alkali enrichment protocol is a membrane mediatedprotocol. By membrane mediated protocol is meant a process or methodwhich employs a membrane at some time during the method. As such,membrane mediated alkali enrichment protocols are those alkalienrichment processes in which a membrane is employed at some time duringthe process. While a given membrane mediated alkali enrichment protocolmay vary, in some instances the membrane mediated protocol includescontacting a first liquid, e.g., a feed liquid, and a second liquid,e.g., a draw liquid, to opposite sides of a membrane. An example of sucha protocol is illustrated in FIG. 1. As can be seen in FIG. 1, first andsecond liquids are flowed past opposite sides of a membrane in a co- orcounter-current fashion, resulting in increased alkalinity of the firstliquid and decreased alkalinity of the second liquid.

Where desired, a thermodynamic force is employed that facilitates thealkalinity increase of the first (i.e., initial) liquid. Any convenientthermodynamic force or combination of forces may be employed, wherethermodynamic driving forces that may be employed include, but are notlimited to: osmotic force, ionic concentration, mechanical pressure,alkalinity, temperature, other chemical reactions, etc., andcombinations thereof, e.g., combinations of osmotic force and mechanicalpressure, e.g., as occurs in pressure assisted forward osmosis.

In some instances, the membrane mediated alkali enrichment protocol isone that employs an osmotic force to facilitate the alkalinityenhancement of the first liquid. Protocols of these embodiments may bereferred to osmotic pressure mediated protocols. The phrase “osmoticpressure mediated protocol ” is employed herein to refer to a processcharacterized by the presence of an osmotic pressure driving force,e.g., in the form of an osmotic pressure gradient, such that a firstliquid (e.g., a draw liquid) of high solute concentration relative tothat of a second liquid (e.g., a feed liquid) is used to induce a netflow of water through a membrane into the first (draw) liquid from thesecond (feed) liquid, thus effectively separating at least a portion ofthe water component of the feed from its solutes. In some embodiments,the draw and feed liquids differ from each other in terms of osmoticpotential, where the osmotic potential of a given draw liquid will behigher than the feed liquid with which it is employed. The magnitude ofthe difference in osmotic potential between a pair of given draw andfeed liquids may vary, and in some instances ranges from 0.1 bar to 150bar, such as 20 bar to 60 bar, including 25 bar to 35 bar. Where themembrane mediated alkali enrichment protocol is an osmotic pressuremediated protocol, the initial liquid from which the enhanced alkalinityliquid is produced may be the draw or feed liquid, as described above.This process is further illustrated in FIG. 2.

The osmotic pressure driving force for the production alkalinity in agiven protocol can be estimated by using the Morse equation, shownbelow.

Osmotic Pressure Driving Force:

πV=inRT

π=osmotic pressure

V=volume/flowrate (assume 1 liter basis)

i=van't Hoff factor

n=concentration (molar/molal)

R=gas constant

T=absolute temp, K

The driving force is the difference in osmotic pressure between the highsalinity (e.g., NaCl) solution and the fresh water solution. The largerthis difference (the larger Δ(i*n)) the larger the driving force ofreaction and larger the yield of alkalinity generation. The osmoticpressure can be used to do work such as driving the unfavorable reactionof NaCl (aq)+H₂O→NaOH (aq)+HCl (aq) by means of diffusion dialysis.

In some instances, the membrane mediated alkali enrichment protocol isone that employs an ionic concentration force to facilitate thealkalinity enhancement of the first liquid. Protocols of theseembodiments may be referred to as ionic concentration mediatedprotocols. The phrase “ionic concentration mediated protocol ” isemployed herein to refer to a process characterized by the presence ofan ionic concentration driving force, e.g., in the form of an ionicconcentration gradient, such that a first liquid of high ionic speciesconcentration relative to that of a second liquid is used to induce anet flow of ions through a membrane from the first liquid into thesecond liquid. In some embodiments, a first liquid may include a highionic strength medium. Such liquids of interest include aqueous mediahaving a salinity of 2 ppt or more, such as 5 ppt or more, including 10ppt or more. In some instances the high ionic strength liquid is anaqueous medium having a salinity that ranges from 3 to 200 ppt, such as5 to 100 ppt. FIG. 3 provides an illustration of how an ionicconcentration mediated protocol is implemented. As shown in FIG. 3, afirst liquid of higher salinity and a second liquid having a salinitylower than that of the first liquid are flowed past opposite sides of amembrane, which may be ion selective, such as described in greaterdetail below. Charge balance forces transport of H⁺ or OH⁻, resulting inmodulation of alkalinity of the two liquids, e.g., increased alkalinityof the feed.

Membrane mediated alkali enrichment protocols may vary, so long as theyproduce an enhanced alkalinity liquid from an initial liquid, asdescribed above. As such, a variety of different types of membranes,membrane configurations, contact protocols, first and second liquidpairings, etc., may be employed, where selection of a particular set ofprotocol parameters may depend on a number of different factors, such asthe nature of the first and second liquids that are available, for whatpurpose the alkali enrichment protocol is employed (e.g., to produce aCO₂ capture liquid, to increase the alkalinity of a CO₂ charged liquid,etc.).

In some embodiments of the methods, a species selective membrane isemployed. For example, in some instances a selective membrane isconfigured or adapted to prevent the passage of CO₂ across the membrane.Accordingly, such selective membranes function as CO₂ barriers thatblock the passage of CO₂, while allowing other ions, e.g., hydrogenions, to cross the membrane. In some instances, the membrane systemincludes a membrane component that is more permissive of Na⁺ transportas compared to Cl⁻ transport. As such, the membrane is configured toallow transfer, e.g., via diffusion, of Na⁺ ions across the membrane ata faster rate relative to the rate at which the membrane allows transferof Cl⁻ ions across the membrane. While the magnitude of the differencein transfer rates of these two ions may vary, in some instances themagnitude of this rate difference ranges from 2 to 1000 fold difference,such as 10 to 100 fold difference. As such when a liquid that includesNa⁺ and Cl⁻ ions is placed on one side of the membrane and a liquid thatincludes relatively less of each of these ions is placed on the otherside of the membrane, the transfer of Na⁺ ions across the membrane fromthe liquid of higher concentration to the liquid of lower concentrationoccurs at a faster rate relative to the transfer of Cl⁻ ions across themembrane from the liquid of higher concentration to the liquid of lowerof concentration. In addition, the membrane system employed in methodsof the invention may be one that is configured to catalyze theproduction of H⁺ and OH⁻ from H₂O, i.e., the membrane system isconfigured to catalyze, e.g., facilitate or enhance, the ionizationwater to produce hydrogen ions and hydroxide ions. As such, when themembrane is contacted with an aqueous liquid, it facilitates or enhancesthe ionization of water molecules in the aqueous liquid.

A variety of different types of membranes may be employed in a givenalkali enrichment protocol. In some embodiments, a selective membranemay utilize dialysis diffusion through the membrane to selectivelypartition ions between the feed and the draw stream. Diffusion dialysismembranes are generally permeable to hydrogen ions and utilizedifferences in ion solubility and mobility within the membrane forselective ion separations between different liquids, e.g., feed and drawliquids. Examples of such membranes include, but are not limited tothose described in: Liu et al., J. Membrane Science (2014) 451: 18-23;Hao et al., J. Membrane Science (2013) 425-426: 156-162; Gu et al.,Desalination (2012) 304: 25-32; and Hao et al., J. Hazardous Materials(2013) 244-245: 348-356; as well as Nafion membranes, e.g., as describedin Okada et al., Electrochimica Acta (1998) 43: 3741-3747. In someinstances, the diffusion dialysis membrane employed is ion or chargeselective membrane, i.e., a membrane that preferentially allows thepassage of one type of charged species across the membrane relative toother species, e.g., other charged species and/or neutral species. Forexample, membranes of interest include cationic membranes, i.e.,membranes that permit the passage of cations but not of anions. Also ofinterest are anionic membranes, i.e., membranes that permit the passageof cations but not of anions. Both cationic and anionic membranes finduse in protocols where alkali enrichment is achieved by removinghydrogen ions from the initial liquid to produce the enhanced alkalinityliquid. In these embodiments, as hydrogen ions are removed from theinitial liquid, the pH of the initial liquid is increased to produce aproduct liquid of enhanced alkalinity relative to the initial liquid. Asreviewed above, the magnitude of the change in pH may vary, and in someinstances ranges from 0.1 to 4 pH units, such as 0.5 to 2.0 pH units.

As reviewed above, in some instances the membrane is an ionicallyselective membrane, e.g., a cationic or anionic membrane. The choice ofwhether to use an anionic or cationic membrane may depend on a number offactors, such as whether the membrane mediated alkali enrichmentprotocol is an osmotic pressure or ionic concentration mediatedprotocol, the nature of the first and second liquids, etc. For example,cationic membrane mediated protocols may be employed where the first andsecond liquids are: (i) a high salinity solution, e.g., 75 ppt NaClsolution, and a fresh water solution, e.g., produced water, (ii) a highsalinity solution and a fresh water solution charged with carbon dioxide(CO₂) gas, e.g., a saturated solution of carbonic acid (H₂CO₃), (iii) ahigh salinity solution and a fresh water solution containing sodiumbicarbonate (NaHCO₃), e.g., 4,500 ppm NaHCO₃.

An example of a cationic membrane mediated protocol is illustrated inFIG. 4. In the protocol illustrated in FIG. 4, diffusion dialysisprinciples powered by osmotic pressure are employed to drive theformation of sodium hydroxide (NaOH) and hydrochloric acid (HCl)energetically uphill from an initial solution of sodium chloride saltwater (NaCl). As illustrated in FIG. 4, two solutions, a concentratedNaCl solution (left of membrane) and a less concentrated, “fresh” watersolution (right of membrane) are brought into contact and separated by acation selective membrane. A cation selective membrane is a diffusiondialysis membrane that is selectively permeable to cations (Na⁺ and H⁺in this case) but is impermeable to negative ions (Cl⁻ and OH⁻ in thiscase). This property allows sodium ions and hydrogen ions to freely passthrough the membrane which can produce sodium hydroxide in the freshwater side and hydrochloric acid in the concentrate side. This processis energetically unfavorable at 18.5 kcal/mol of monovalentcharge-balanced exchange. However, the concentrate NaCl solution, havinga larger salinity than the fresh solution, generates an osmotic pressurewhich makes sodium/hydrogen ion transfer energetically favorable. Thisallows the reaction to continue until the osmotic pressure is relievedby the removal of sodium ions and the concurrent generation of sodiumhydroxide solution. This sodium hydroxide solution contains alkalinitywhich can then be used in a later stage, e.g., to sequester CO₂ from aflue gas in the form of bicarbonate ion, such as described in greaterdetail below.

FIG. 5 provides a view of a variation of the cationic membrane mediatedprotocol illustrated in FIG. 4. Alkalinity generation is limited both bythe work stored as osmotic pressure dictated by the difference in ionconcentration between the two contacted liquids and by the expensiveproduction of OH⁻ alkalinity. If carbon dioxide is dissolved in thefresh solution (right side), then the generated alkalinity can take theform of a CO₂ (aq)→HCO₃ ⁻ transition. This approach requiressignificantly less energy at 7 kcal/mol of sodium/hydrogen ion exchangethan the production of an OH⁻ ion from water. This approach isillustrated in FIG. 5, where alkalinity is generated as CO₂ is beingsequestered and the resulting product is not a solution for future CO₂sequestering (i.e., is not a CO₂ capture liquid), as in protocolillustrated in FIG. 4, but rather is a solution with CO₂ alreadysequestered in the form of sodium bicarbonate (NaHCO₃). This solutioncan be combined at a later stage with other cations to form usefulmineral products such as CaCO₃ or MgCO₃, e.g., as described in greaterdetail below.

The same diffusion dialysis technique can be further employed togenerate alkalinity to convert bicarbonate ion (HCO₃ ⁻) to carbonate ion(CO₃ ²⁻). A schematic is shown in FIG. 6. As illustrated in FIG. 6, eachsodium/hydrogen ion exchange is energetically unfavorable at 11.5kcal/mol. This is more favorable than the production of raw NaOH butless favorable than the conversion of CO₂ (aq)→HCO₃ ⁻. As long as theNaCl concentrate solution (left) has a high salinity, the reactionshould partially proceed and convert bicarbonate ion to carbonate ion.The product in this case is a carbon dioxide capture solution and can beused at a later date to sequester CO₂ from flue gas. The energeticsillustrated in the figure were determined by comparing the Gibbs freeenergy of formation of the products and reactants on a liter, molarbasis.

Any cationic membrane may be employed in cationic membrane mediatedalkali enrichment protocols. Cationic membranes of interest include, butare not limited to: Selemion™ cation exchange membranes CMV, CMD, HSF,CSO, CMF, and the like. A specific cationic membrane mediated protocolis illustrated in FIG. 7, wherein a Nafion™ Membrane(tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acidcopolymer) is employed as the cationic membrane. As shown in FIG. 7, theinitial liquid is a feed liquid having a pH of 5.4 and a lower salinitythan that of the draw liquid. The output is a product liquid of enhancedalkalinity, i.e., pH 7.8.

As described above, the choice of whether to use an anionic or cationicmembrane may depend on a number of factors, such as whether the membranemediated alkali enrichment protocol is an osmotic pressure or ionicconcentration mediated protocol, the nature of the first and secondliquids, etc. For example, anionic membrane mediated protocols may beemployed where the first and second liquids are: (i) a high salinitysolution, e.g., 60 ppt NaCl solution, and a fresh water solution, e.g.,produced water, (ii) a high salinity solution charged with carbondioxide (CO₂) gas, e.g., 60 ppt NaCl solution saturated with carbonicacid (H₂CO₃), and a fresh water solution, e.g. produced water. Anionicmembranes of interest include, but are not limited to: Selemion™ anionexchange membranes AMV, AMT, DSV, AAV, ASV, AHO, APS4, and the like.Examples of anionic membrane mediated alkali enrichment protocols areillustrated in FIGS. 8 and 9.

Membranes employed in membrane mediated alkali enrichment protocols mayvary with respect to porosity. In some embodiments, employed membranesmay be size-based separators that allow molecules under a certain sizeto pass through, while preventing larger molecules from passing through.In this way, the membranes can be used to selectively retain moleculesthat are over a certain size while allowing other molecules that arebelow a certain size to pass through. In some embodiments, employedmembranes include pores that range in size from 1 micron up to 2microns, up to 3 microns, up to 4 microns, up to 5 microns, up to 6microns, up to 7 microns, up to 8 microns, up to 9 microns, or up to 10microns or more.

In some embodiments, the membrane may include pores ranging in size from1 Angstrom up to 10 Angstroms, up to 20 Angstroms, up to 30 Angstroms,up to 40 Angstroms, up to 50 Angstroms, up to 60 Angstroms, up to 70Angstroms, up to 80 Angstroms, up to 90 Angstroms, up to 100 Angstroms,up to 200 Angstroms, up to 300 Angstroms, up to 400 Angstroms, up to 00Angstroms, up to 600 Angstroms, up to 700 Angstroms, up to 800Angstroms, up to 900 Angstroms or more. In some embodiments, themembrane includes a reverse osmosis membrane having pores ranging insize from 5 Angstroms up to 6 Angstroms, up to 7 Angstroms, up to 8Angstroms.

In some embodiments, the selective membrane may be a nano-filtrationmembrane, such as a membrane having pores ranging in size from 1nanometer to 2 nanometers. In some embodiments, the selective membranemay include an ultra-filtration membrane, such as a membrane havingpores ranging in size from 10 nanometers up to 20 nanometers, up to 30nanometers, up to 40 nanometers, up to 50 nanometers, up to 60nanometers, up to 70 nanometers, up to 80 nanometers, up to 90nanometers, up to 100 nanometers, up to 125 nanometers, up to 150nanometers, up to 175 nanometers, up to 200 nanometers, or more.

In some embodiments, the membrane may contain catalysts to aid in thesolubility and mobility of waters and ions within the membrane. Thecatalysts may hasten chemical reactions which further aid in theselective partitioning of waters and ions between the feed and the drawsolutions. For example, the membrane systems employed in methods of theinvention may include a metal particle composite membrane system. As themembranes are metal particle composite membranes, they include a metalparticle component and a membrane component, which components may bestably associated with each other to provide the composite membrane. Ofinterest as membrane components are membranes that are configured toprovide for ion transport across the membrane using adehydration/resolvation mechanism, as opposed to a size exclusionmechanism. In other words, membranes of interest are membranes that areconfigured to provide for dehydration/resolvation mediated iontransport, in contrast to size exclusion ion transport. With respect toions that are transported by the membrane, as reviewed above, membranesof interest are those that provide for relatively fast Na⁺ diffusionrelative to Cl⁻. Other ions that that may be transported across themembrane at a relatively faster rate than Cl⁻ include potassium ion(K+), hydrogen ions and hydroxide ions, etc. Other ions that may betransported across the membrane at a rate approximating or less than Cl⁻include sulfate ions (SO₄ ²⁻), Nitrogen oxides (nitrates, nitrites),bicarbonates, carbonates and etc. In some instances, the membrane is onethat provides for little, if any, transport of dissolved inorganiccarbon (DIC), i.e., the membrane provides for little, if any, transportof CO₂, carbonic acid, bicarbonate ion and carbonate.

The metal particle component of such membranes is made up of apopulation of metal particles that are stably associated with themembrane component. By stably associated is meant that the metalparticles do not dissociate from the membrane component under conditionsof use in the methods of the invention, e.g., as described herein. Themetal particles may be stably associated with the membrane component inany desired manner, such as being embedded in the membrane matrix, beingpresent on the surface of the membrane matrix, etc., and combinationsthereof. The metal particles may be covalently or non-covalently (e.g.,ionic or electrostatically) bonded to the membrane component to providefor the desired stable association using any convenient protocol, wherebonding protocols of interest include, but are not limited to, thosedescribed in published PCT Publication No. WO2012/166701, the disclosureof which is herein incorporated by reference.

The metal particles may range in size. The diameter of the particles mayvary, ranging in some instances from a single nanometer to severalmicrons. As such, in some instances the particles have a diameterranging from 1 to 10,000 nm, such as 5 to 5,000 nm, including 10 to1,000 nm. In some instances, the metal particles are metalnanoparticles, ranging in diameter from 1 to 1,000 nm, such as 5 to 750nm, including 10 to 500 nm. A given metal particle component may besubstantially homogeneous with respect to the diameter or size of theparticles which make up the component, or may include a variety ofdifferent particle sizes, as desired. The metal particles may include avariety of different metals, or alloys or oxides thereof. Metalparticles of interest are particles that catalyze the ionization ofwater into the hydrogen ions and hydroxide ions, e.g., as describedabove. Metals of interest include, but are not limited to: gold,platinum, palladium, nickel, cobalt, manganese, chromium, silver,copper, iron, ruthenium, rhodium, zinc, and alloys and oxides thereof.(See e.g., Chen et al., A first principles study of water dissociationon small copper clusters. Physical chemistry chemical physics : PCCP 12,9845 (Sep. 7, 2010); Wang et al., A systematic theoretical study ofwater dissociation on clean and oxygen-preadsorbed transition metals.Journal of Catalysis 244, 10 (Nov. 15, 2006)). A given metal particlecomponent may be substantially homogeneous with respect to the metal ofthe particles which make up the component, or may include a variety ofdifferent metal species, as desired. The mass ratio of metal componentto membrane component in the composite membrane may vary so long as theamount of metal particles present in the membrane component issufficient to catalyze the ionization of water to a desired extent(e.g., a measurable extent), ranging in some instances from 5:1 to1:100, such as 2:1 to 1:2.

FIG. 10 provides an illustration of a composite metal particle membranein accordance with an embodiment of the invention. The compositemembrane shown in FIG. 10 includes a hydrated polymer, such as polyvinylalcohol (PVA) or cellulose acetate (CA). Embedded within the membraneare metallic nanoparticles that catalyze the ionization of water, suchas nickel or zinc. The membrane is relatively impervious to CO₂ (aq),quickly permeable to Na⁺, very slowly permeable to Cl⁻ and has veryquick OH⁻, and H⁺ transport. The important products produced uponcontact with a first aqueous liquid and a second aqueous liquid areNaHCO₃ on the base side and HCl on the acid side. Metal particlecomposite membranes of interest, e.g., as described above, are furtherdescribed in U.S. Patent Application Ser. No. 62/056,377 filed on Sep.26, 2014, the disclosure of which is herein incorporated by reference.

A given membrane may have a variety of different physical dimensions. Insome instances, membranes of interest having thicknesses ranging from0.001 mm to 1 mm, such as 0.005 mm to 0.05 mm and including 0.03 mm to0.3 mm. Membranes in accordance with embodiments of the invention canhave a variety of configurations including thin films, hollow fibermembranes, spiral wound membranes, monofilaments and disk tubes.Membranes of interest can be made of organic or inorganic materials. Insome embodiments, membranes made of materials such as cellulose acetate,cellulose nitrate, polysulfone, polyvinylidene fluoride, polyamide andacrylonitrile co-polymers may be used. Other membranes may be mineralmembranes or ceramic membranes made of materials such as ZrO₂ and TiO₂.The material selected for use as the membrane may be selected to be ableto withstand various process conditions to which the membrane may besubjected. For example, it may be desirable that the membrane be able towithstand elevated temperatures, such as those associated withsterilization or other high temperature processes. In some embodiments,a membrane module may be operated at a temperature in the range of 0 to100° C., such as 40 to 50° C. Likewise, the membrane may be selected tobe able to maintain integrity under various pH conditions, such as a pHlevel ranging from 2 to 11, such as 7 to 10. The thickness of themembrane may vary, ranging in some instances from 0.01 mm to 0.1 mm,such as 0.02 mm to 0.06 mm and including 0.03 mm to 0.04 mm.

Membranes employed in methods of the invention may be present indistinct alkali enrichment units, which units are configured produce adesired amount of alkalinity per time. For example, alkali enrichmentunits may be configured to produce 0.1 to 10 moles of alkalinity persquare meter of membrane per hour (mol alkalinity/m² h), such as 0.5 to1.5 mol alkalinity/m² h. A given unit may include one or more squaremeter (m²) of membrane, such as two or more m² membrane, e.g., 5 m² to500,000 m² membrane, such as 40 m² to 400 m² membrane, including 50,000m² to 250,000 m² membrane, which may be arranged so that the first andsecond fluids flow sequentially past each of the membranes, e.g., in aco- or counter-current fashion. In such units, the one or m² membranemay be positioned within a housing or casing, e.g., in a plate-and-framestructure or “stack”. The housing may be sized and shaped to accommodatethe membrane(s) positioned therein. For example, the housing may besubstantially cylindrical if housing spirally wound forward osmosismembranes. Alternatively, the housing may have a box configuration,e.g., where multiple membranes are arranged therein in a stacked orplate-and-frame structure. The housing of the membrane module maycontain inlets to provide first and second liquids to the membranemodule as well as outlets for withdrawal of product streams from themembrane module. In some embodiments, the housing may provide at leastone reservoir or chamber for holding or storing a fluid to be introducedto or withdrawn from the membrane module. In some embodiments, thehousing may be insulated.

In accordance with one or more embodiments, the alkali enrichmentprotocol may be performed using a forward osmosis separation system,which may be constructed and arranged so as to bring a first liquid anda second liquid into contact with first and second sides of a membrane(such as described above), respectively. Although the first and secondliquids can remain stagnant, in some instances both the first and secondliquids are introduced by cross flow, i.e., flows parallel to thesurface of the membrane. This configuration may increase membranesurface area contact along one or more fluid flow paths, therebyincreasing the efficiency of the forward osmosis. In some embodiments,the first and second solutions may flow in the same direction. In otherembodiments, the first and second solutions may flow in oppositedirections. In at least some embodiments, similar fluid dynamics mayexist on both sides of a membrane surface. This may be achieved bystrategic integration of the one or more forward osmosis membranes inthe module or housing.

The conditions of the alkali enrichment step may vary as desired. Thetemperature of the liquids may vary, ranging in some instances from 0 to100° C., such as 4 to 80° C. The temperatures of the liquids may be thesame or different. When different, the magnitude of any temperaturevariation may vary, ranging in some instances from 0.1 to 95° C., suchas 30 to 45° C. The pressure of the liquids may also vary, ranging insome instances from 1 to 30 bar, such as 1.5 to 2 bar. When different,the magnitude of any pressure variation may vary, ranging in someinstances from 0.1 to 30 bar, such as 0.5 to 1 bar. The flow rates ofthe liquids may be the same or different, and in some instances rangefrom 0.25 to 10 gallon/min, such as 0.5 to 1 gallon/min. When different,the magnitude of any flow rate variation between the draw and feed mayvary, and in some instances ranges from 0.05 to 9.75 gallon/min, such as1 to 3 gallon/min. Forward osmosis mediated alkali enrichment protocols(also referred to sometimes as alkali recovery protocols) are furtherdescribed in United States Provisional Application Ser. No. 61/990,486filed on May 8, 2014, the disclosure of which is herein incorporated byreference.

The nature of the first (i.e., initial) and second liquids that areprocessed in methods of the invention may vary. The initial liquid maybe any liquid for which an increase in alkalinity is desired. Theinitial liquid may be an aqueous medium that may vary depending on thespecific protocol being performed. Aqueous media of interest includepure water (e.g., fresh water) as well as water that includes one ormore solutes, e.g., divalent cations, e.g., Ca²⁺, Mg²⁺, Be²⁺, Ba²⁺,Sr²⁺, counterions, e.g., carbonate, hydroxide, etc. The aqueous mediummay be a naturally occurring or man-made medium, as desired. Naturallyoccurring aqueous media include, but are not limited to, waters obtainedfrom seas, oceans, lakes, swamps, estuaries, lagoons, brines, geologicalbrines, alkaline lakes, inland seas, brackish waters, etc. Man-madesources of aqueous media may also vary, and may include brines producedby water desalination plants, waste waters, and the like. First andsecond liquid pairings of interest include, but are not limited to:fresh and salt water (e.g., river water and seawater), salt water anddesalination waste water (e.g., RO retentate), fresh water charged withCO₂-containing gas, e.g., industrial flue gas, and salt water, freshwater and salt water charged with CO₂-containing gas, e.g., industrialflue gas, acidic salt water and fresh water and the like, or anycombination of the waters disclosed herein.

In some embodiments, the first liquid is a carbonate buffered aqueousmedium. Carbonate buffered aqueous media employed in methods of theinvention include liquid media in which a carbonate buffer is present.As such, liquid aqueous media of interest include dissolved CO₂, water,carbonic acid (H₂CO₃), bicarbonate ions (HCO₃ ⁻), hydrogen ions (H⁺) andcarbonate ions (CO₃ ²⁻). The constituents of the carbonate buffer in theaqueous media are governed by the equation:

CO₂+H₂O

H₂CO₃

H⁺+HCO₃ ⁻

2H⁺+CO₃ ²⁻

Where desired, the initial liquid may be one that has been contactedwith a CO²⁻ containing gas. In words, the initial liquid is one to whicha gaseous source of CO₂ has been contacted such that the initial liquidthat is subjected to the alkali enrichment protocol is one that includesan amount of dissolved inorganic carbon (DIC), i.e., it is a CO₂ chargedliquid. In such instances, the CO₂ charged liquid includes an amount ofdissolved CO₂. The amount of CO₂ dissolved in the liquid may vary, andin some instances ranges from 0.05 to 40 mM, such as 1 to 35 mM,including 25 to 30 mM. In this case, a CO₂ capture solution can begenerated based on carbonate ion alkalinity. In some instances,carbonate ion alkalinity will be 100 mM or greater, such as 250 mM, andincluding 500-1,000 mM, or more. Such instances are described in greaterdetail below.

The second liquid employed in methods of the invention may vary. In someinstances, the second liquid differs from the first liquid in terms ofosmotic potential, where the osmotic potential of a given second liquidmay be higher or lower relative to the initial liquid with which it isemployed, depending on the particular alkali recover protocol that isused (e.g., as described above). The magnitude of the difference inosmotic potential between any two given liquid pairs may vary, and insome instances ranges from 0.1 bar to 150 bar, such as 20 bar to 60 bar,including 25 bar to 35 bar.

Any convenient liquid may be employed as the second liquid. In someembodiments, a second liquid may include a high ionic strength medium.In some embodiments, the second liquid contains non-hydrogen monovalentcations that are capable of crossing the membrane system to provide forcharge balance and thereby facility in the alkalinity increase of thefirst liquid. In certain embodiments, the non-hydrogen monovalentcations include, but are not limited to: Na+, K+, and NH₄ ⁺. Secondliquids of interest include aqueous media having a salinity of 2 ppt ormore, such as 5 ppt or more, including 10 ppt or more. In some instancesthe second liquid is an aqueous medium having a salinity that rangesfrom 3 to 50 ppt, such as 5 to 35 ppt. The pH of the second liquid mayvary, and in some instances ranges from 4 to 12, such as 5 to 10 andincluding 6 to 9. In some instances, the second liquid may be referredto as a brine draw liquid. The term “brine” refers to water saturated ornearly saturated with salt and has a salinity that is 50 ppt (parts perthousand) or greater, such as 60 ppt or greater, and including 95 ppt orgreater. Brine draw liquids of interest include, but are not limited to:man-made brines, such as geothermal plant wastewaters, oil fieldproduced brines, fracking operation produced waters, desalination wastewaters, etc., as well as natural brines, such as surface brines found inbodies of water on the surface of the earth and deep brines, foundunderneath the earth, as well as other liquids having a salinity asdescribed above. In some embodiments, a draw liquid includes ageological brine or a brine discharge from a desalination plant.

As reviewed above, the second or draw liquid employed in the alkalienrichment protocol may vary. One type of draw liquid that may beemployed is concrete production wash water, where the phrase “concreteproduction wash water” refers to wash water from concrete plants,trucks, etc. Concrete production wash water may be obtained from avariety of sources, including but not limited to: rinsing a ready-mixconcrete truck after it has returned from a site project. Such washwaters may have pH in the range of 8-13, such as pH 9-10 or pH 11-12.Concrete production wash waters may contain commercial chemicaladmixtures for concrete, such as, but not limited to, chemicaladmixtures that comply with ASTM designation C494 or ASTM designationC260, that contain organic alkalinity such as, but not limited to,primary, secondary and tertiary amines, etc. Concrete production washwaters may also contain, in addition to chemical admixtures forconcrete, dissolved metal cations, for example, dissolved monovalentalkali metal cations such as Lithium (Li⁺), sodium (Na⁺) or potassium(K⁺), dissolved alkaline earth metal cations such as calcium (Ca²⁺), orother dissolved metal cations such as aluminum (Al³⁺) or iron (Fe²⁺,Fe³⁺). The positively charged cations may be charged-balanced withnegatively charged anions such as, but not limited to, monovalentbicarbonate (HCO₃ ⁻), chloride (Cl⁻), hydroxide (OH⁻) or nitrate (NO₃ ⁻)ions, as well as divalent sulfate (SO₄ ²⁻) ions. The pH of and thealkalinity available in the concrete production wash water may bereflected by the weight percent of calcium oxide (CaO) present in thecement used at the concrete plant. The cement may be 50-75 weightpercent (wt %) CaO, such as but not limited to 51-59 wt % CaO or 61-67wt % CaO. Based on the ready-mix concrete formulation mentioned above, aconcrete plant that uses cement that is 65 wt % CaO has 390 lb CaO percubic yard of concrete. Treating CaO with water produces calciumhydroxide (Ca(OH)₂), which has a solubility limit of 0.185 parts Ca(OH)₂per 100 parts water (at 100° C.). If, for example, a ready-mix concretetruck returned to the concrete plant with two cubic yards of concreteleft over from a project, and the truck were rinsed with, e.g., 500gallons of water, the resulting wash water would have 954 lb Ca(OH)₂alkalinity (Calculation: (390 lb CaO/yd³)×(2 yd³)/(56.08 gCaO/mol)×(74.10 g Ca(OH)₂/mol)×(0.185 parts/100 parts)×(500 parts)=954lb Ca(OH)₂).

Introduction of the first liquid and the second liquid into a membranesystem, e.g., as described above, results in the production of a productliquid (i.e., enhanced alkalinity liquid) from the first liquid, wherethe product liquid has an increased alkalinity as compared to the firstliquid, i.e., the product liquid is an enhanced alkalinity liquid. Assummarized above, while the increase in alkalinity may vary, in someinstances the magnitude of the increase in pH ranges from 0.1 to 10,such as 1 to 9, including 2.5 to 7.5, e.g.,3 to 7. While the pH of theproduct liquid may vary, in some instances the pH of the product liquidranges from 5 to 14, such as 6 to 13, including 7 to 12, e.g.,8 to 11.

In addition, methods of the invention may produce an acidic by-productliquid. The acidic by-product liquid may vary, and is one that isproduced from the second. The pH of the acidic by-product liquid rangesin some instances from 0 to 8, such as 3 to 5. The nature of the acidicby-product liquid may vary, where in some instances the acidicby-product liquid includes HCl.

Alkali enrichment protocols and systems for practicing the same that maybe adapted for use methods of the invention, e.g., as described above,include those described in U.S. Patent Application No. 61/990,486 filedon May 8, 2014 and U.S. Patent Application Ser. No. 62/051,100 filed onSep. 16, 2014; the disclosures of which are herein incorporated byreference.

As indicated above, an alkali enrichment protocol (e.g., as describedabove) may be employed at one or more times during a CO₂ sequestrationprocess, e.g., in producing a CO₂ capture liquid, to increase thealkalinity of a CO₂ contacted liquid (i.e., a liquid that includesdissolved inorganic carbon derived from CO₂), etc. Examples of differentmethods in which an alkali enrichment protocol is employed at differenttimes are described in greater detail in the context of specificembodiments as illustrated by the accompanying figures.

CO₂/CO₂ Capture Liquid Contact

As indicated above, embodiments of methods as described herein include astep of contacting a gaseous source of CO₂ with a liquid underconditions sufficient for CO₂ molecules in the gas to dissolve into theliquid and thereby be separated from the gas, e.g., to produce a liquidcondensed phase (LCP) containing liquid. As such, aspects of suchembodiments include contacting a CO₂ containing gas with an aqueousmedium to remove CO₂ from the CO₂ containing gas.

The CO₂-containing gas that is contacted with the CO₂ sequestrationliquid to produce the high DIC containing liquid may be pure CO₂ or becombined with one or more other gasses and/or particulate components,depending upon the source, e.g., it may be a multi-component gas (i.e.,a multi-component gaseous stream). While the amount of CO₂ in suchgasses may vary, in some instances the CO₂-containing gases have a pCO₂of 10³ or higher, such as 10⁴ Pa or higher, such as 10⁵ Pa or higher,including 10⁶ Pa or higher. The amount of CO₂ in the CO₂-containing gas,in some instances, may be 20,000 or greater, e.g., 50,000 ppm orgreater, such as 100,000 ppm or greater, including 150,000 ppm orgreater, e.g., 500,000 ppm or greater, 750,000 ppm or greater, 900,000ppm or greater, up to and including 1,000,000 ppm or greater (in pureCO₂ exhaust the concentration is 1,000,000 ppm) and in some instancesmay range from 10,000 to 500,000 ppm, such as 50,000 to 250,000 ppm,including 100,000 to 150,000 ppm. The temperature of the CO₂-containinggas may also vary, ranging in some instances from 0 to 1800° C., such as100 to 1200° C. and including 600 to 700° C.

In some instances, a CO₂-containing gas is not pure CO₂, in that itcontains one or more additional gasses and/or trace elements. Additionalgasses that may be present in the CO₂-containing gas include, but arenot limited to water, nitrogen, mononitrogen oxides, e.g., NO, NO₂, andNO₃, oxygen, sulfur, monosulfur oxides, e.g., SO, SO₂ and SO₃), volatileorganic compounds, e.g., benzo(a)pyrene C₂OH₁₂, benzo(g,h,l)peryleneC₂₂H₁₂, dibenzo(a,h)anthracene C₂₂H₁₄, etc. Particulate components thatmay be present in the CO₂-containing gas include, but are not limited toparticles of solids or liquids suspended in the gas, e.g., heavy metalssuch as strontium, barium, mercury, thallium, etc.

In certain embodiments, CO₂-containing gases are obtained from anindustrial plant, e.g., where the CO₂-containing gas is a waste feedfrom an industrial plant. Industrial plants from which theCO₂-containing gas may be obtained, e.g., as a waste feed from theindustrial plant, may vary. Industrial plants of interest include, butare not limited to, power plants and industrial product manufacturingplants, such as but not limited to chemical and mechanical processingplants, refineries, cement plants, steel plants, etc., as well as otherindustrial plants that produce CO₂ as a byproduct of fuel combustion orother processing step (such as calcination by a cement plant). Wastefeeds of interest include gaseous streams that are produced by anindustrial plant, for example as a secondary or incidental product, of aprocess carried out by the industrial plant.

Of interest in certain embodiments are waste streams produced byindustrial plants that combust fossil fuels, e.g., coal, oil, naturalgas, as well as man-made fuel products of naturally occurring organicfuel deposits, such as but not limited to tar sands, heavy oil, oilshale, etc. In certain embodiments, power plants are pulverized coalpower plants, supercritical coal power plants, mass burn coal powerplants, fluidized bed coal power plants, gas or oil-fired boiler andsteam turbine power plants, gas or oil-fired boiler simple cycle gasturbine power plants, and gas or oil-fired boiler combined cycle gasturbine power plants. Of interest in certain embodiments are wastestreams produced by power plants that combust syngas, i.e., gas that isproduced by the gasification of organic matter, e.g., coal, biomass,etc., where in certain embodiments such plants are integratedgasification combined cycle (IGCC) plants. Of interest in certainembodiments are waste streams produced by Heat Recovery Steam Generator(HRSG) plants. Waste streams of interest also include waste streamsproduced by cement plants. Cement plants whose waste streams may beemployed in methods of the invention include both wet process and dryprocess plants, which plants may employ shaft kilns or rotary kilns, andmay include pre-calciners. Each of these types of industrial plants mayburn a single fuel, or may burn two or more fuels sequentially orsimultaneously. A waste stream of interest is industrial plant exhaustgas, e.g., a flue gas. By “flue gas” is meant a gas that is obtainedfrom the products of combustion from burning a fossil or biomass fuelthat are then directed to the smokestack, also known as the flue of anindustrial plant.

Where the CO₂ containing gas is a multi-component gaseous medium thatincludes CO₂ and other gases, e.g., as described above, the CO₂containing gas may be processed to increase the partial pressure of CO₂in the gas prior to contact with the CO₂ capture liquid. In suchinstances, the magnitude of increase of the CO₂ in the CO₂ containinggas may vary, where in some instances the increase may be 5% (v/v) ormore, such as 10% (v/v) or more, 20% (v/v) or more, 25%(v/v) or more ormore, 50% (v/v) or more, 75% (v/v) or more, including 80 to 90% (v/v) ormore. For example, where the gaseous components of non-treated flue gasinput stream contain <1 -20% (v/v) CO₂, the gaseous stream may beprocessed to produce a treated flue gas output stream that contains30-90% (v/v) CO₂. While separation of non-CO₂ components from a gaseousstream may be accomplished using any convenient protocol, in someinstances a membrane mediated gas separation protocol is employed. Whilesuch protocols may vary, a number of CO₂ selective membrane mediated gasseparation protocols may be used, including but not limited to: thosedescribed in Ramasubramian et al., “Membrane processes for carboncapture from coal-fired power plant flue gas: A modeling and coststudy,” J. Membrane Science (2012) 421-422: 299-310; Published PCTApplication Serial No. WO/2006/050531 titled “Membranes, Methods OfMaking Membranes, And Methods Of Separating Gases Using Membranes” andplastic-based, nano-engineered membranes (e.g., from Membrane ResearchGroup (MEMFO) at the Chemical Engineering Department of the NorwegianUniversity of Science and Technology (NTNU)) as described in Biopact at“http://news.mongabay.com/bioenergy/2007/09/new-plastic-based-nano-engineered-co2.html”;the disclosures of which are herein incorporated by reference.

The aqueous medium that is contacted with the gaseous source of CO₂(i.e., the CO₂ containing gas) may vary, ranging from fresh water tobicarbonate buffered aqueous media. Bicarbonate buffered aqueous mediaemployed in embodiments of the invention include liquid media in which abicarbonate buffer is present. As such, liquid aqueous media of interestinclude dissolved CO₂, water, carbonic acid (H₂CO₃), bicarbonate ions(HCO₃ ⁻), protons (H⁺) and carbonate ions (CO₃ ²⁻). The constituents ofthe bicarbonate buffer in the aqueous media are governed by theequation:

CO₂+H₂O

H₂CO₃

H⁺+HCO₃ ⁻

2H⁺+CO₃ ²⁻

The pH of the bicarbonate buffered aqueous media may vary, ranging insome instances from 7 to 11, such as 8 to 11, e.g., 8 to 10, including 8to 9. In some instances, the pH ranges from 8.2 to 8.7, such as from 8.4to 8.55. The bicarbonate buffered aqueous medium may be a naturallyoccurring or man-made medium, as desired. Naturally occurringbicarbonate buffered aqueous media include, but are not limited to,waters obtained from seas, oceans, lakes, swamps, estuaries, lagoons,brines, alkaline lakes, inland seas, etc. Man-made sources ofbicarbonate buffered aqueous media may also vary, and may include brinesproduced by water desalination plants, and the like. Of interest in someinstances are waters that provide for excess alkalinity, which isdefined as alkalinity that is provided by sources other than bicarbonateion. In these instances, the amount of excess alkalinity may vary, solong as it is sufficient to provide 1.0 or slightly less, e.g., 0.9,equivalents of alkalinity. Waters of interest include those that provideexcess alkalinity (meq/liter) of 30 or higher, such as 40 or higher, 50or higher, 60 or higher, 70 or higher, 80 or higher, 90 or higher, 100or higher, etc. Where such waters are employed, no other source ofalkalinity, e.g., NaOH, is required.

In some instances, the aqueous medium that is contacted with the CO₂containing gas is one which, in addition to the bicarbonate bufferingsystem (e.g., as described above), further includes an amount ofdivalent cations. Inclusion of divalent cations in the aqueous mediumcan allow the concentration of bicarbonate ion in the bicarbonate richproduct to be increased, thereby allowing a much larger amount of CO₂ tobecome sequestered as bicarbonate ion in the bicarbonate rich product.In such instances, bicarbonate ion concentrations that exceed 5,000 ppmor greater, such as 10,000 ppm or greater, including 15,000 ppm orgreater may be achieved. For instance, calcium and magnesium occur inseawater at concentrations of 400 and 1200 ppm respectively. Through theformation of a bicarbonate rich product using seawater (or an analogouswater as the aqueous medium), bicarbonate ion concentrations that exceed10,000 ppm or greater may be achieved.

In such embodiments, the total amount of divalent cation source in themedium, which divalent cation source may be made up of a single divalentcation species (such as Ca²⁺) or two or more distinct divalent cationspecies (e.g., Ca²⁺, Mg²⁺, etc.), may vary, and in some instances is 100ppm or greater, such as 200 ppm or greater, including 300 ppm orgreater, such as 500 ppm or greater, including 750 ppm or greater, suchas 1,000 ppm or greater, e.g., 1,500 ppm or greater, including 2,000 ppmor greater. Divalent cations of interest that may be employed, eitheralone or in combination, as the divalent cation source include, but arenot limited to: Ca²⁺, Mg²⁺, Be²⁺, Ba²⁺, Sr²⁺, Pb²⁺, Fe²⁺, Hg²⁺ and thelike. Other cations of interest that may or may not be divalent include,but are not limited to: Na⁺, K⁺, NH⁴⁺, and Li⁺, as well as cationicspecies of Mn, Ni, Cu, Zn, Cu, Ce, La, Al, Y, Nd, Zr, Gd, Dy, Ti, Th, U,La, Sm, Pr, Co, Cr, Te, Bi, Ge, Ta, As, Nb, W, Mo, V, etc. Naturallyoccurring aqueous media which include a cation source, divalent orotherwise, and therefore may be employed in such embodiments include,but are not limited to: aqueous media obtained from seas, oceans,estuaries, lagoons, brines, alkaline lakes, inland seas, etc.

In some instances, the aqueous medium is one that has been subjected toan alkali enrichment process, such as a membrane mediated alkalienrichment process, e.g., as described above. Alkali enrichmentprocesses of interest include, but are not limited to, those describedin U.S. Patent Application Ser. Nos. 61/990,486 filed on May 8, 2014;62/051,100 filed on Sep. 16, 2014 and 62/056,377 filed on Sep. 26, 2014;the disclosures of which are herein incorporated by reference.

In some instances, the divalent cations are not present in anysubstantial amount in the liquid that is contacted with the CO² gas. Inthese embodiments, the amount of divalent cations, if any, that ispresent, is such as to not give rise to measureable scaling in theCO₂/liquid contactor. In some embodiments of these methods, the aqueousmedium may be softened prior to hydrogen ion removal. In other words, aninitial aqueous medium may be subject to a hardness reduction protocolprior to being subjected to a hydrogen ion removal protocol, e.g., asdescribed above. Hardness reduction protocols of interest includeremoving divalent cations, e.g., alkaline earth metal divalent cations,from an initial aqueous medium.

While any convenient hardness reduction protocol may be employed, insome instances the hardness reduction protocol includes contacting aninitial aqueous medium with a divalent cation selective membrane underconditions sufficient to remove at least a portion of the divalentcations from the initial aqueous medium. Divalent cation selectivemembranes that may be used in embodiments of the invention areconfigured or adapted to prevent the passage of divalent cations fromone side of the membrane to the other, while allowing liquid and smallermolecules (e.g., molecules having a diameter that is smaller than thediameter of a hydrdated divalent cation) to pass from one side of themembrane to the other. Divalent cation selective membranes in accordancewith embodiments of the invention have pores or passages of a size thatallows liquid and smaller molecules to pass through, but prevents orblocks the passage of particles having a size equal to or greater thanthe diameter of a hydrated divalent cation, including but not limitedto: Ca²⁺, Mg²⁺, Be²⁺, Ba²⁺, Sr²⁺, Pb²⁺, Fe²⁺, Hg²⁺.

In some embodiments, an aqueous medium membrane feed is contacted with adivalent cation selective membrane under conditions that are sufficientto separate the liquid component of the feed and smaller moleculeshaving a diameter that is less than that of a hydrated divalent cationfrom the retentate. Processing conditions may include a range ofpositive or negative pressures applied to the membrane. Where desired,positive or negative pressure may be applied to the membrane such that apressure differential is established across the membrane. For example,in some embodiments, a membrane feed is contacted with a divalent cationselective membrane such that a pressure differential across the membraneranges from 1 atmosphere (ATM) up to 50 ATM, such as 20-30 ATM isestablished.

In some embodiments, processing conditions may include a range ofsuitable temperatures. For example, in some embodiments, a membrane feedis contacted with a divalent cation selective membrane at a temperatureranging from 0° C. up to 100° C., such as 40-50° C. Likewise, a membranemay be selected to be able to maintain integrity under various pHconditions, such as a pH ranging from 2 to 11, such as 7 to 10.

Contacting the aqueous medium with the divalent cation selectivemembrane results in the formation of a permeate having a reducedconcentration of divalent cations relative to the feed, and a retentatehaving an increased concentration of divalent cations relative to thefeed. Aspects of the methods involve subjecting the reduced divalentcation concentration permeate to the hydrogen ion removal processdescribed above. Aspects of the methods also involve subjecting theincreased divalent cation concentration retentate to further processing,as described below.

In some embodiments, the divalent cation selective membrane is ananofiltration membrane. By “nanofiltration membrane” is meant amembrane whose pores range in diameter from 1 to 10 Angstroms, such as 5to 8 Angstroms, and are configured to retain divalent cations, such asMg²⁺ and Ca²⁺ cations, in the retentate, while allowing smaller speciesto pass through the membrane with the permeate. For example, in certainembodiments, a nanofiltration membrane is adapted to retain hydrateddivalent cations (e.g., Ca²⁺, Mg²⁺) on a first side of the membrane,while allowing smaller hydrated monovalent ions to pass to the otherside of the membrane. In some embodiments, a nanofiltration membrane isconfigured such that in use, the nanofiltration membrane can retaindivalent cations in the retentate without adding additional ions, suchas sodium ions, to the feed. In some embodiments, a nanofiltrationmembrane is configured such that in use, the nanofiltration membrane canretain divalent cations in the retentate without the need tocontinuously heat or cool the solution.

Nanofiltration membranes in accordance with embodiments of the inventionmay have varying pore density, and in some instances have a pore densityranging from 1 to 150 pores per square centimeter, such as 50 to 100pores per square centimeter. The pore dimensions and pore density may becontrolled using suitable process conditions, such as controlled pH,temperature and process timing employed during a nanofiltration membranefabrication process.

The material from which a nanofiltration membrane is made may beselected to be able to withstand various process conditions to which themembrane may be subjected during processing. For example, it may bedesirable that the membrane be able to withstand elevated temperatures,such as those associated with sterilization or other high temperatureprocesses, as well as elevated pressures.

In some embodiments, a nanofiltration membrane has a standardizeddesign, such as, e.g., a spiral wound module design or a tubular moduledesign, having a range of standard diameters to fit standard pressurevessel sizes and/or components thereof. In certain embodiments, astandardized nanofiltration membrane module is configured to facilitatethe connection of multiple membrane modules in series and/or in parallelwithin a standardized pressure vessel.

In some embodiments, a nanofiltration membrane may be in the form of acartridge that is positioned within a housing or casing. The housing maybe sized and shaped to accommodate the membrane(s) positioned therein.For example, the housing may be substantially cylindrical if housing aspirally wound membrane. The housing of the module may contain inlets orchannels to facilitate the introduction of a membrane feed into themodule, as well as outlets for withdrawal of product streams from themodule. In some embodiments, the housing may provide at least onereservoir or chamber for holding or storing a fluid to be introducedinto or withdrawn from the module. In some embodiments, the housing maybe insulated.

Protocols for softening an aqueous medium are further described inUnited States Provisional Application Serial No. 62/051,100 filed onSep. 16, 2014; the disclosure of which is herein incorporated byreference.

Contact of the CO₂ containing gas and bicarbonate buffered aqueousmedium is done under conditions sufficient to remove CO₂ from the CO₂containing gas (i.e., the CO₂ containing gaseous stream), and increasethe dissolved inorganic carbon (including bicarbonate ion) concentrationof the aqueous medium. The CO₂ containing gas may be contacted with theaqueous medium using any convenient protocol. For example, contactprotocols of interest include, but are not limited to: direct contactingprotocols, e.g., bubbling the gas through a volume of the aqueousmedium, concurrent contacting protocols, i.e., contact betweenunidirectionally flowing gaseous and liquid phase streams,countercurrent protocols, i.e., contact between oppositely flowinggaseous and liquid phase streams, and the like. Contact may beaccomplished through use of infusers, bubblers, fluidic Venturireactors, spargers, gas filters, sprays, trays, packed column reactors,aqueous froth filters (e.g., as described in U.S. Pat. Nos. 7,854,791;6,872,240; 6,616,733, as well as Published U.S. Patent Application Nos.20140245887 and WO2005/014144; the disclosures of which are hereinincorporated by reference); and the like, as may be convenient. Theprocess may be a batch or continuous process.

In some instances, the gaseous source of CO₂ is contacted with theliquid using a microporous membrane contactor. Microporous membranecontactors of interest include a microporous membrane present in asuitable housing, where the housing includes a gas inlet and a liquidinlet, as well a gas outlet and a liquid outlet. The contactor isconfigured so that the gas and liquid contact opposite sides of themembrane in a manner such that molecule may dissolve into the liquidfrom the gas via the pores of the microporous membrane. The membrane maybe configured in any convenient format, where in some instances themembrane is configured in a hollow fiber format. Hollow fiber membranereactor formats which may be employed include, but are not limited to,those described in U.S. Pat. Nos. 7,264,725; 6,872,240 and 5,695,545;the disclosures of which are herein incorporated by reference. In someinstances, the microporous hollow fiber membrane contactor that isemployed is a Liqui-Cel® hollow fiber membrane contactor (available fromMembrana, Charlotte N.C.), which membrane contactors includepolypropylene membrane contactors and polyolefin membrane contactors.

Contact between the capture liquid and the CO₂-containing gas occursunder conditions such that a substantial portion of the CO₂ present inthe CO₂-containing gas goes into solution, e.g., to produce bicarbonateions. By substantial portion is meant 10% or more, such as 50% or more,including 80% or more.

The temperature of the capture liquid that is contacted with theCO₂-containing gas may vary. In some instances, the temperature rangesfrom −1.4 to 100° C., such as 20 to 80° C. and including 40 to 70° C. Insome instances, the temperature may range from −1.4 to 50° C. or higher,such as from −1.1 to 45° C. or higher. In some instances, coolertemperatures are employed, where such temperatures may range from −1.4to 4° C., such as −1.1 to 0° C. In some instances, warmer temperaturesare employed. For example, the temperature of the capture liquid in someinstances may be 25° C. or higher, such as 30° C. or higher, and may insome embodiments range from 25 to 50° C., such as 30 to 40° C.

The CO₂-containing gas and the capture liquid are contacted at apressure suitable for production of a desired CO₂ charged liquid. Insome instances, the pressure of the contact conditions is selected toprovide for optimal CO₂ absorption, where such pressures may range from1 ATM to 100 ATM, such as 1 to 50 ATM, e.g., 20-30 ATM or 1 ATM to 10ATM. Where contact occurs at a location that is naturally at 1 ATM, thepressure may be increased to the desired pressure using any convenientprotocol. In some instances, contact occurs where the optimal pressureis present, e.g., at a location under the surface of a body of water,such as an ocean or sea. In some instances, contact of theCO₂-containing gas and the alkaline aqueous medium occurs a depth belowthe surface of the water (e.g., the surface of the ocean), where thedepth may range in some instances from 10 to 1000 meters, such as 10 to100 meters. In some instances, the CO₂ containing gas and CO₂ captureliquid are contacted at a pressure that provides for selectiveabsorption of CO₂ from the gas, relative to other gases in the CO₂containing gas, such as N₂, etc. In these instances, the pressure atwhich the CO₂ containing gas and capture liquid are contacted may vary,ranging from 1 to 100 atmospheres (atm), such as 1 to 10 atm andincluding 20 to 50 atm.

Contact between the alkaline aqueous medium and the CO₂-containing gasresults in the production of a DIC containing liquid. As such, incharging the CO₂ capture liquid with CO₂, a CO₂ containing gas may becontacted with CO₂ capture liquid under conditions sufficient to producedissolved inorganic carbon (DIC) in the CO₂ capture liquid , i.e., toproduce a DIC containing liquid. The DIC is the sum of theconcentrations of inorganic carbon species in a solution, represented bythe equation: DIC=[CO₂*]+[HCO₃ ⁻]+[CO₃ ²⁻], where [CO₂*] is the sum ofcarbon dioxide ([CO₂]) and carbonic acid ([H₂CO₃]) concentrations, [HCO₃³¹ ] is the bicarbonate concentration and [CO₃ ²⁻] is the carbonateconcentration in the solution. The DIC of the aqueous media may vary,and in some instances may be 5,000 ppm or greater, such as 10,000 ppm orgreater, including 15,000 ppm or greater. In some instances, the DIC ofthe aqueous media may range from 5,000 to 20,000 ppm, such as 7,500 to15,000 ppm, including 8,000 to 12,000 ppm. The amount of CO₂ dissolvedin the liquid may vary, and in some instances ranges from 0.05 to 40 mM,such as 1 to 35 mM, including 25 to 30 mM. The pH of the resultant DICcontaining liquid may vary, ranging in some instances from 4 to 12, suchas 6 to 11 and including 7 to 10, e.g., 8 to 8.5.

In some instances where the gaseous source of CO₂ is a multicomponentgaseous stream, contact occurs in a manner such that such that CO₂ isselectively absorbed by the CO₂ absorbing aqueous medium. By selectivelyabsorbed is meant that the CO₂ molecules preferentially go into solutionrelative to other molecules in the multi-component gaseous stream, suchas N₂, O₂, Ar, CO, H₂, CH₄ and the like.

Where desired, the CO₂ containing gas is contacted with the captureliquid in the presence of a catalyst (i.e., an absorption catalyst,either hetero- or homogeneous in nature) that mediates the conversion ofCO₂ to bicarbonate. Of interest as absorption catalysts are catalyststhat, at pH levels ranging from 8 to 10, increase the rate of productionof bicarbonate ions from dissolved CO₂. The magnitude of the rateincrease (e.g., as compared to control in which the catalyst is notpresent) may vary, and in some instances is 2-fold or greater, such as5-fold or greater, e.g., 10-fold or greater, as compared to a suitablecontrol. In some instances, the catalyst is a carbon dioxide-specificcatalyst. Examples of carbon dioxide-specific catalysts of interestinclude enzymes, such as carbonic anhydrases, synthetic catalysts, suchas those transition metal catalysts described in Koziol et al., “Towarda Small Molecule, Biomimetic Carbonic Anhydrase Model: Theoretical andExperimental Investigations of a Panel of Zinc(II) Aza-MacrocyclicCatalysts,” Inorganic Chemistry (2012) 51: 6803-6812, colloidal metalparticles, such as those described in Bhaduri and Siller, “Nickelnanoparticles catalyse reversible hydration of carbon dioxide formineralization carbon capture and storage,” Catalysis Science &Technology (2013) DOI: 10.1039/c3cy20791a, and the like, e.g., colloidalmetal oxide particles. Carbonic anhydrases of interest include bothnaturally occurring (i.e., wild-type) carbonic anhydrase, as well asmutants thereof. Specific carbonic anhydrases of interest include, butare not limited to: α-CAs, which include mammalian carbonic anhydrases,e.g., the cytosolic CAs (CA-I, CA-II, CA-III, CA-VII and CA XIII) (CA1,CA2, CA3, CA7, CA13), mitochondrial CAs (CA-VA and CA-VB) (CA5A, CA5B),secreted CAs (CA-VI) (CA6), and membrane-associated CAs (CA-IV, CA-IX,CA-XII, CA-XIV and CA-XV) (CA4, CA9, CA12, CA14); β-CAs, which includeprokaryotic and plant chloroplast CAs; y-CAs, e.g., such as found inmethane-producing bacteria; and the like. Carbonic anhydrases ofinterest further include those described in U.S. Pat. No. 7,132,090, thedisclosure of which is herein incorporated by reference. Carbonicanhydrases of interest include those having a specific activity of 10³s⁻¹ or more, such as 10⁴ s⁻¹ to or more, including 10⁵ s⁻¹ or more. Whenemployed, the catalyst is present in amount effective to provide for thedesired rate increase of bicarbonate production, e.g., as describedabove. In some instances where the catalyst is an enzyme, the activityof the enzyme in the aqueous media may range from 10³ to 10⁶ s⁻¹, suchas 10³ to 10⁴ s⁻¹ and including 10⁵ to 10 ⁶ s⁻¹. When employed, acatalyst, e.g., enzyme such as a carbonic anhydrase, can be madeavailable in the reaction using any convenient approach, such as througha solid support (such as a permeable membrane) to which the catalyst isattached or otherwise with which the catalyst is stably associated,through porous media and the like having the catalyst stably associatedtherewith, large surfaces with the catalyst immobilized therein (i.e.,attached thereto), or with the catalyst in solution, e.g., which may berecovered following use. Examples of catalyst formats that may beemployed include, but are not limited to, those described in U.S. Pat.No. 7,132,090; the disclosure of which is herein incorporated byreference. Synthetic catalysts of interest include syntheticallyprepared transition metal containing complexes, prepared as biomimeticmodels of carbonic anhydrase enzymes, e.g., as described above. Specificsynthetic catalysts include, but are not limited to: transition metalaza-macrocyclic catalysts, e.g., the zinc(II) aza-macrocyclic catalystshaving macrocyclic rings of 9, 12, 13, or 14, as described in Koziol etal., “Toward a Small Molecule, Biomimetic Carbonic Anhydrase Model:Theoretical and Experimental Investigations of a Panel of zinc(II)Aza-Macrocyclic Catalysts,” Inorganic Chemistry (2012) 51: 6803-6812,imidazole- and indole-based metal catalysts, e.g., the zinc(II)catalysts described in United States Published Application No.US20110293496, United States Published Application No. US20120199535 andUnited States Published Application No. US20110151537,aminopyridyl-based catalysts, e.g., as described in Feng et al., “AHighly Reactive Mononuclear Zn(II) Complex for Phosphodiester Cleavage,”Journal of the American Chemical Society (2005) 127: 13470-13471,pyrazolylhydroborato- and pyridylthiomethyl-based compounds, e.g., asdescribed in Sattler and Parkin, “Structural characterization of zincbicarbonate compounds relevant to the mechanism of action of carbonicanhydrase,” Chemical Science (2012) 3: 2105-2109. Synthetic catalysts ofinterest include those having a specific activity of 10² or more, suchas 10³ s⁻¹ or more, including 10⁴ s⁻¹ or more. When employed, thesynthetic catalyst is present in amount effective to provide for thedesired rate increase of bicarbonate production, e.g., as describedabove for carbonic anhydrase. When employed, a synthetic catalyst, e.g.,aza-macrocyclic transition metal catalyst, can be made available in thereaction using any convenient approach, e.g., as described above forcarbonic anhydrase. Metal nanoparticles of interest include commerciallyavailable as well as synthetically prepared colloidal particles oftransition metals. Specific colloidal metal particles include, but arenot limited to: metal nanoparticles, e.g., the nickel nanoparticles(NiNPs) described in Bhaduri and Siller, “Nickel nanoparticles catalysereversible hydration of carbon dioxide for mineralization carbon captureand storage,” Catalysis Science & Technology (2013) DOI:10.1039/c3cy20791a. Colloidal metal particles of interest include thosehaving a specific activity of 10² s⁻¹ or more, such as 10 ³ s⁻¹ or more,including 10⁴ s⁻¹ or more. When employed, the colloidal metal particlesare present in amount effective to provide for the desired rate increaseof bicarbonate production, e.g., as described above for carbonicanhydrase. When employed, the colloidal metal particles, e.g.,transition metal nanoparticles, can be made available in the reactionusing any convenient approach, e.g., as described above for carbonicanhydrase. Metal nanoparticle catalysts finding use in embodimentsdescribed herein are further described in U.S. Provisional ApplicationSerial No. 61/793,585 filed on Mar. 15, 2013; the disclosure of which isherein incorporated by reference. Catalysts of interest are furtherdescribed in U.S. patent application Ser. No. 14/112,495; the disclosureof which is herein incorporated by reference.

In some embodiments, the resultant CO₂ charged liquid is abicarbonate-containing liquid, where in in some instances, thebicarbonate-containing liquid is a two phase liquid which includesdroplets of a liquid condensed phase (LCP) in a bulk liquid, e.g., bulksolution. By “liquid condensed phase” or “LCP” is meant a phase of aliquid solution which includes bicarbonate ions wherein theconcentration of bicarbonate ions is higher in the LCP phase than in thesurrounding, bulk liquid.

LCP droplets are characterized by the presence of a meta-stablebicarbonate-rich liquid precursor phase in which bicarbonate ionsassociate into condensed concentrations exceeding that of the bulksolution and are present in a non-crystalline solution state. The LCPcontains all of the components found in the bulk solution that isoutside of the interface. However, the concentration of the bicarbonateions is higher than in the bulk solution. In those situations where LCPdroplets are present, the LCP and bulk solution may each containion-pairs and pre-nucleation clusters (PNCs). When present, the ionsremain in their respective phases for long periods of time, as comparedto ion-pairs and PNCs in solution.

The bulk phase and LCP are characterized by having different K_(eq),different viscosities, and different solubilities between phases.Bicarbonate, carbonate, and divalent ion constituents of the LCPdroplets are those that, under appropriate conditions, may aggregateinto a post-critical nucleus, leading to nucleation of a solid phase andcontinued growth. While the association of bicarbonate ions withdivalent cations, e.g., Ca²⁺, in the LCP droplets may vary, in someinstances bidentate bicarbonate ion/divalent cation species may bepresent. For example, in LCPs of interest, Ca²⁺/bicarbonate ionbidentate species may be present. While the diameter of the LCP dropletsin the bulk phase of the LCP may vary, in some instances the dropletshave a diameter ranging from 1 to 500 nm, such as 10 to 100 nm. In theLCP, the bicarbonate to carbonate ion ratio, (i.e., the HCO₃ ⁻/CO₃²⁻ratio) may vary, and in some instances is 10 or greater to 1, such as20 or greater to 1, including 25 or greater to 1, e.g., 50 or greaterto 1. Additional aspects of LCPs of interest are found in Bewernitz etal., “A metastable liquid precursor phase of calcium carbonate and itsinteractions with polyaspartate,” Faraday Discussions. 7 Jun. 2012. DOI:10.1039/c2fd20080e (2012) 159: 291-312. The presence of LCPs may bedetermined using any convenient protocol, e.g., the protocols describedin Faatz et al., Advanced Materials, 2004, 16, 996-1000; Wolf et al.,Nanoscale, 2011, 3, 1158-1165; Rieger et al., Faraday Discussions, 2007,136, 265-277; and Bewernitz et al., Faraday Discussions, 2012, 159,291-312.

Where the bicarbonate-containing solution has two phases, e.g., asdescribed above, the first phase may have a higher concentration ofbicarbonate ion than a second phase, where the magnitude of thedifference in bicarbonate ion concentration may vary, ranging in someinstances from 0.1 to 4, such as 1 to 2. For example, in someembodiments, a bicarbonate rich product may include a first phase inwhich the bicarbonate ion concentration ranges from 1000 ppm to 5000ppm, and a second phase where the bicarbonate ion concentration ishigher, e.g., where the concentration ranges from 5000 ppm to 6000 ppmor greater, e.g., 7000 ppm or greater, 8000 ppm or greater, 9000 ppm orgreater, 10,000 ppm or greater, 25,000 ppm or greater, 50,000 ppm orgreater, 75,000 ppm or greater, 100,000 ppm, 500,000 or greater.

Where desired, following production of the LCP containing liquid, theresultant LCP containing liquid may be manipulated to increase theamount or concentration of LCP droplets in the liquid. As such,following production of the bicarbonate containing liquid, thebicarbonate containing liquid may be further manipulated to increase theconcentration of bicarbonate species and produce a concentratedbicarbonate liquid. In some instances, the bicarbonate containing liquidis manipulated in a manner sufficient to increase the pH. In suchinstances, the pH may be increased by an amount ranging from 0.1 to 6 pHunits, such as 1 to 3 pH units. The pH of the concentrated bicarbonateliquid of such as step may vary, ranging in some instances from 5.0 to13.0, such as 6.5 to 8.5. The concentration of bicarbonate species inthe concentrated bicarbonate liquid may vary, ranging in some instancesfrom 1 to 1000 mM, such as 20 to 200 mM and including 50 to 100 mM. Insome instances, the concentrated bicarbonate liquid may further includean amount of carbonate species. While the amount of carbonate speciesmay vary, in some instances the carbonate species is present in anamount ranging from 0.01 to 800 mM, such as 10 to 100 mM. The pH of thebicarbonate liquid may be increased using any convenient protocol. Insome instances, an electrochemical protocol may be employed to increasethe pH of the bicarbonate liquid to produce the concentrated bicarbonateliquid. Electrochemical protocols may vary, and in some instancesinclude those employing an ion exchange membrane and electrodes, e.g.,as described in U.S. Pat. Nos. 8,357,270; 7,993,511; 7,875,163; and7,790,012; the disclosures of which are herein incorporated byreference. Alkalinity of the bicarbonate containing liquid may also beaccomplished by adding a suitable amount of a chemical agent to thebicarbonate containing liquid. Chemical agents for effecting protonremoval generally refer to synthetic chemical agents that are producedin large quantities and are commercially available. For example,chemical agents for removing protons include, but are not limited to,hydroxides, organic bases, super bases, oxides, ammonia, and carbonates.Hydroxides include chemical species that provide hydroxide anions insolution, including, for example, sodium hydroxide (NaOH), potassiumhydroxide (KOH), calcium hydroxide (Ca(OH)₂), or magnesium hydroxide(Mg(OH)₂). Organic bases are carbon-containing molecules that aregenerally nitrogenous bases including primary amines such as methylamine, secondary amines such as diisopropylamine, tertiary such asdiisopropylethylamine, aromatic amines such as aniline, heteroaromaticssuch as pyridine, imidazole, and benzimidazole, and various formsthereof. In some embodiments, an organic base selected from pyridine,methylamine, imidazole, benzimidazole, histidine, and a phophazene isused to remove protons from various species (e.g., carbonic acid,bicarbonate, hydrogen ion, etc.) for precipitation of precipitationmaterial. In some embodiments, ammonia is used to raise pH to a levelsufficient to precipitate precipitation material from a solution ofdivalent cations and an industrial waste stream. Super bases suitablefor use as proton-removing agents include sodium ethoxide, sodium amide(NaNH₂), sodium hydride (NaH), butyl lithium, lithium diisopropylamide,lithium diethylamide, and lithium bis(trimethylsilyl)amide. Oxidesincluding, for example, calcium oxide (CaO), magnesium oxide (MgO),strontium oxide (SrO), beryllium oxide (BeO), and barium oxide (BaO) arealso suitable proton-removing agents that may be used.

Another type of further manipulation following production that may beemployed is a dewatering of the initial barcarbonate containing liquidto produce a concentrated bicarbonate containing liquid, e.g., aconcentrated LCP liquid. Dewatering may be accomplished using anyconvenient protocol, such as via contacting the LCP composition with asuitable membrane, such as an ultrafiltration membrane, to remove waterand certain species, e.g., NaCl, HCl, H₂CO₃ but retain LCP droplets,e.g., as described in greater detail in U.S. application Ser. No.14/112,495; the disclosure of which is herein incorporated by reference.

As described above, catalysts may be employed in some embodiments, e.g.,where a carbonic anhydrase (CA) is employed to increase the rate ofreaction whereby gaseous carbon dioxide (CO₂) and water convert tobicarbonate (HCO₃ ⁻) ion and a proton (H⁺), or vice versa. Whendissolved in aqueous solution, for example, in a solution used as acarbon capture solution and having an alkalinity concentration in therange of, for example, 1-2,000 millimolar (mM) equivalents, such as butnot limited to 5-50, 75-800 or 900-2,200 mM alkalinity equivalents, CAsignificantly increases the rate of formation of HCO₃ ⁻ upon contactingthe solution with, for example, flue gas from an industrial emitterwhere the partial pressure of CO₂ in the flue gas is, for example,0.1-99.9% by weight, such as but not limited to 0.5-1.5%, 4.0-17% or45-98% CO2 by weight. Because the molecular mass of CA enzymes is on theorder of kilodaltons (kDa), for example, 1-70 kDa, such as but notlimited to 4-8, 15-30 or 45-65 kDa, soluble CA may be recovered bypassing the solution through a membrane filtration system, for example,loose reverse osmosis membrane systems, nanofiltration membrane systemsor tight ultrafiltration systems, that reject CA but pass solutions richin HCO₃ ⁻ ion, such as bicarbonate-rich liquid condensed phase (LCP)solutions as described above. The reject solution from the membranesystem, one that contains the rejected CA, may be recirculated asdesired in the process so as to continuously increase the rate of CO₂conversion to HCO₃ ⁻ from contacting the capture liquid with a CO₂containing gas. The permeate solution from the membrane system, e.g.,one that contains the passed LCP, may be further concentrated asdesired, e.g., through a membrane filtration system (such as describedabove), for example, a nanofiltration membrane system, then used in amineralization process, e.g., as described below.

Where desired, the bicarbonate containing liquid (which may or may notbe concentrated such as described above) may be stored for an extendedperiod of time, if not indefinitely, thereby sequestering CO₂ obtainedfrom the initial CO₂ source used to produce charge the feedwater. Forexample, in cold climates the bicarbonate containing liquid may beallowed to freeze until weather conditions allow the product to thaw, atwhich time further manipulation of the product (e.g., as describedbelow) may be performed. Product bicarbonate liquid compositions may bestored in geologic reservoirs until needed, or even allowed to mix withgeologic brine solutions and allowed to mineralize in situ. As such,following the production of a bicarbonate containing liquid, furthermanipulation (if it occurs at all), may be delayed for a period of time,such as 6 hours or longer, 12 hours or longer, 1 day or longer, 1 weekor longer, 1 month or longer, 3 months or longer, 6 months or longer, 1year or longer, etc. In instances where storage of the bicarbonatecontaining liquid is desired, the product may be stored in a sealedcontainer, e.g., a drum or larger container, and may or may not bestored in an environment that includes an atmosphere which preventsoff-gassing, e.g., a pure CO₂ atmosphere, etc.

In some instances, the product BRP compositions are employed asbicarbonate additives for cements. The term “bicarbonate additive” asused herein means any composition, which may be liquid or solid, thatincludes bicarbonate (HCO₃ ⁻) ions, or a solid derivative thereof (e.g.,as described in greater detail below). Where the bicarbonate additive isa liquid composition, the liquid composition may be employed as the solesetting liquid component in production of the settable cementitiouscomposition, or it may be employed in conjunction with one or moreadditional setting liquids, e.g., as described in greater detail below.The pH of a liquid bicarbonate additive may vary, and in certaininstances ranges from 4 to 12, such as 5 to 9, e.g., 6 to 8. The amountof bicarbonate ions in the bicarbonate additive may vary, as desired.For liquid compositions, the overall amount of bicarbonate may range insome instances from 0.1 wt. % to 30 wt. %, such as 3 to 20 wt. %,including from 10 to 15 wt. %.

As mentioned above, the bicarbonate additive employed to produce a givensettable cementitious composition may be a liquid or solid. When presentas a solid, the solid is a dehydrated version of a liquid bicarbonateadditive. The solid may be one that is produced from a liquidbicarbonate additive using any convenient protocol for removed waterfrom the liquid, e.g., evaporation, freeze drying, etc. Upon combinationwith a suitable volume of water, the resultant solid dissolves in thewater to produce a liquid bicarbonate additive, e.g., as describedabove. In some instances, reconstitution is achieved by combining thedry bicarbonate additive with a sufficient amount of liquid, e.g.,aqueous medium, such as water, where the liquids to solids ratioemployed may vary, and in some instances ranges from 1,000,000 to 1,such as 100,000 to 10. Solid bicarbonate additives may include a varietyof different particle sizes and particle size distributions. Forexample, in some embodiments a solid bicarbonate additive may includeparticulates having a size ranging from 1 to 10,000 μm, such as 10 to1,000 μm and including 50 to 500 μm.

Further details regarding BRP bicarbonate additives are provided in U.S.application Ser. No. 14/112,495 filed on Oct. 17, 2013; the disclosureof which is herein incorporated by reference.

CO₂ Sequestering Carbonate Production

Following preparation of the bicarbonate-containing solution (as well asany storage thereof, as desired, e.g., as described above), thebicarbonate-containing solution or component thereof (e.g., LCP) may bemanipulated to produce solid phase carbonate compositions, and thereforesequester CO₂ from the initial CO₂-containing gas into a solid form andproduce a CO₂ sequestering carbonate material. By CO₂ sequesteringcarbonate material is meant a material that stores a significant amountof CO₂ in a storage-stable format, such that CO₂ gas is not readilyproduced from the material and released into the atmosphere. In certainembodiments, the CO₂-sequestering material includes 5% or more, such as10% or more, including 25% or more, for instance 50% or more, such as75% or more, including 90% or more of CO₂, e.g., present as one or morecarbonate compounds. The CO₂-sequestering materials produced inaccordance with methods of the invention may include one or morecarbonate compounds, e.g., as described in greater detail below. Theamount of carbonate in the CO₂-sequestering material, e.g., asdetermined by coulometry, may be 40% or higher, such as 70% or higher,including 80% or higher.

CO₂ sequestering materials, e.g., as described herein, provide forlong-term storage of CO₂ in a manner such that CO₂ is sequestered (i.e.,fixed) in the material, where the sequestered CO₂ does not become partof the atmosphere. When the material is maintained under conditionsconventional for its intended use, the material keeps sequestered CO₂fixed for extended periods of time (e.g., 1 year or longer, 5 years orlonger, 10 years or longer, 25 years or longer, 50 years or longer, 100years or longer, 250 years or longer, 1000 years or longer, 10,000 yearsor longer, 1,000,000 years or longer, or even 100,000,000 years orlonger) without significant, if any, release of the CO₂ from thematerial. With respect to the CO₂-sequestering materials, when they areemployed in a manner consistent with their intended use and over theirlifetime, the amount of degradation, if any, as measured in terms of CO₂gas release from the product will not exceed 10% per year, such as 5%per year, and in certain embodiments, 1% per year. In some instances,CO₂-sequestering materials provided by the invention do not release morethan 1%, 5%, or 10% of their total CO₂ when exposed to normal conditionsof temperature and moisture, including rainfall of normal pH, for thereintended use, for at least 1, 2, 5, 10, or 20 years, or for more than 20years, for example, for more than 100 years. Any suitable surrogatemarker or test that is reasonably able to predict such stability may beused. For example, an accelerated test comprising conditions of elevatedtemperature and/or moderate to more extreme pH conditions is reasonablyable to indicate stability over extended periods of time. For example,depending on the intended use and environment of the composition, asample of the composition may be exposed to 50, 75, 90, 100, 120, or150° C. for 1, 2, 5, 25, 50, 100, 200, or 500 days at between 10% and50% relative humidity, and a loss less than 1%, 2%, 3%, 4%, 5%, 10%,20%, 30%, or 50% of its carbon may be considered sufficient evidence ofstability of materials of the invention for a given period (e.g., 1, 10,100, 1000, or more than 1000 years).

In certain instances of such embodiments, the bicarbonate-containingliquid or component thereof (e.g., LCP) is combined with a divalentcation source. Any convenient divalent cation source may be employed.Divalent cations, such as alkaline earth metal cations, e.g., calciumand magnesium cations, are of interest. Cation sources of interestinclude, but are not limited to, the brine from water processingfacilities, such as sea water desalination plants, brackish waterdesalination plants, groundwater recovery facilities, wastewaterfacilities, and the like, which produce a concentrated stream ofsolution high in cation contents. Also of interest as cation sources arenaturally occurring sources, such as, but not limited to, nativeseawater and geological brines, which may have varying cationconcentrations and may also provide a ready source of cations to triggerthe production of carbonate solids from a bicarbonate rich product orcomponent thereof (e.g., LCP), such as described in greater detailbelow. The cation source employed in such solid carbonate productionsteps may be the same as or different from the aqueous media employed inthe bicarbonate rich product production step, e.g., as described below.

In some instances, the divalent cation source is a concentrated hardwater source, where the concentrated hard water is one that has beenproduced by contacting an initial hard water with a divalent cationselective membrane to produce a concentrated hard water that has anincreased concentration of divalent cations as compared to the initialhard water. Divalent cation selective membranes that may be used in suchembodiments are configured or adapted to prevent the passage of divalentcations from one side of the membrane to the other, while allowingliquid and smaller molecules (e.g., molecules having a diameter that issmaller than the diameter of a hydrdated divalent cation) to pass fromone side of the membrane to the other. Divalent cation selectivemembranes in accordance with embodiments of the invention have pores orpassages of a size that allows liquid and smaller molecules to passthrough, but prevents or blocks the passage of particles having a sizeequal to or greater than the diameter of a hydrated divalent cation,such as Ca²⁺ or Mg²⁺. A membrane “feed” refers to an initial liquidmixture that is applied to a membrane filter. A membrane “retentate” or“concentrate” refers to the components of the feed that cannot passthrough the pores or passages of the membrane and are thus retained onthe first side of the membrane. A membrane “permeate” refers to thecomponents of the feed that are able to pass through the pores orpassages of the membrane to reach the other side of the membrane. Insome embodiments of the methods, a membrane feed is contacted with adivalent cation selective membrane under conditions that are sufficientto separate the liquid component of the feed and smaller moleculeshaving a diameter that is less than that of a hydrated divalent cationfrom the retentate. Processing conditions may include a range ofpositive or negative pressures applied to the membrane. Where desired,positive or negative pressure may be applied to the membrane such that apressure differential is established across the membrane. For example,in some embodiments, a membrane feed is contacted with a divalent cationselective membrane such that a pressure differential across the membraneranges from 1 atmosphere (atm) up to 40 atm, such as 20-30 atm isestablished. In some embodiments, processing conditions may include arange of suitable temperatures. For example, in some embodiments, amembrane feed is contacted with a divalent cation selective membrane ata temperature ranging from 0° C. up to 100° C., such as 40-50° C.Likewise, a membrane may be selected to be able to maintain integrityunder various pH conditions, such as a pH ranging from 2 to 11, such as7 to 10. In some embodiments, the selective membrane is a nanofiltrationmembrane. By “nanofiltration membrane” is meant a membrane whose poresrange in diameter from 1 to 10 Angstroms and are configured to retaindivalent cations, such as Mg²⁺ and Ca²⁺ cations, in the membraneretentate, while allowing smaller ions to pass through the membrane withthe membrane permeate. For example, in certain embodiments,nanofiltration membranes are adapted to retain hydrated divalent cations(e.g., Ca²⁺, Mg²⁺) on a first side of the membrane, while allowingsmaller hydrated monovalent ions to pass to the other side of themembrane. In some embodiments, a nanofiltration membrane is configuredsuch that in use, the nanofiltration membrane can facilitate theformation of a concentrated hard water without adding additional ions,such as sodium ions, to the solution. In some embodiments, ananofiltration membrane is configured such that in use, thenanofiltration membrane can facilitate the formation of a concentratedhard water without the need to continuously heat or cool the solution.Nanofiltration membranes in accordance with embodiments of the inventionmay have varying pore density, and in some instances have a pore densityranging from 1 to 150 pores per square centimeter. The pore dimensionsand pore density may be controlled using suitable process conditions,such as controlled pH, temperature and process timing employed during ananofiltration membrane fabrication process. The material from which ananofiltration membrane is made may be selected to be able to withstandvarious process conditions to which the membrane may be subjected duringprocessing. For example, it may be desirable that the membrane be ableto withstand elevated temperatures, such as those associated withsterilization or other high temperature processes, as well as elevatedpressures. In some embodiments, a nanofiltration membrane has astandardized design, such as, e.g., a spiral wound module design or atubular module design, having a range of standard diameters to fitstandard pressure vessel sizes and/or components thereof. In certainembodiments, a standardized nanofiltration membrane module is configuredto facilitate the connection of multiple membrane modules in seriesand/or in parallel within a standardized pressure vessel. In someembodiments, a nanofiltration membrane may be in the form of a cartridgethat is positioned within a housing or casing. The housing may be sizedand shaped to accommodate the membrane(s) positioned therein. Forexample, the housing may be substantially cylindrical if housing aspirally wound membrane. The housing of the module may contain inlets orchannels to facilitate the introduction of a membrane feed into themodule, as well as outlets for withdrawal of product streams from themodule. In some embodiments, the housing may provide at least onereservoir or chamber for holding or storing a fluid to be introducedinto or withdrawn from the module. In some embodiments, the housing maybe insulated. Examples of commercially-available nanofiltrationmembranes include, but are not limited to, those available from avariety of commercial vendors, e.g., Nitto (Hydranautics), Dow (DowFilmTec); General Electric (GE Osmonics), etc. As used herein, the term“concentrated hard water” means a solution of aqueous media having adivalent cation concentration of 500 ppm or greater, such as 600 ppm orgreater, including 750 ppm or greater. In some instances, a concentratedhard water has a divalent cation concentration of 2,500 ppm or greater,e.g., 5,000 ppm or greater, 10,000 ppm or greater, 15,000 ppm orgreater, 20,000 ppm or greater, 25,000 ppm or greater, 30,000 ppm orgreater, 40,000 ppm or greater, including 50,000 ppm or greater. In someembodiments, a concentrated hard water may have a divalent cationconcentration ranging from 500 to 200,000 ppm, such as 1,000 to 200,000ppm, where in some instances the concentration ranges from 50,000 to200,000 ppm, such as 50,000 to 175,000 ppm, an including 50,000 to150,000 ppm. While the concentrated hard water may vary depending on theparticular application, concentrated hard waters of interest include oneor more solutes, e.g., divalent cations, such as alkaline earth metalcations, including but not limited to Mg²⁺, Ca²⁺, Be²⁺, Ba²⁺, Sr²⁺,Pb²⁺, Fe²⁺, and Hg²⁺. The pH of concentrated hard waters in accordancewith embodiments of the invention may vary, and in some instances rangesfrom 2 to 12, such as 4 to 10. In such embodiments, an initial hardwater may be naturally occurring or man-made, as desired. Naturallyoccurring hard waters include, but are not limited to, waters obtainedfrom seas, oceans, lakes, swamps, estuaries, lagoons, brines, alkalinelakes, inland seas, etc. In certain embodiments, a naturally occurringhard water source is co-located with a location where a CO₂sequestration protocol or process is conducted. Man-made sources of hardwaters may also vary, and may include brines produced by waterdesalination plants, mining operations, such as fracking operations, oilfield operations, industrial waste waters, and the like. Of interest insome instances are waters that provide for excess alkalinity, which isdefined as alkalinity which is provided by sources other thanbicarbonate ion. In these instances, the amount of excess alkalinity mayvary, so long as it is sufficient to provide 1.0 or slightly less, e.g.,0.9, equivalents of alkalinity. Hard waters of interest include thosethat provide excess alkalinity (meq/liter) of 30 or higher, such as 40or higher, 50 or higher, 60 or higher, 70 or higher, 80 or higher, 90 orhigher, 100 or higher, etc. In certain embodiments, where such hardwaters are employed, no other source of alkalinity, e.g., NaOH, isrequired. Where desired, methods of such embodiments may includecombining a scaling-retarding amount of an acidic solution with theconcentrated hard water. Acidic solutions in accordance with embodimentsof the invention may be, e.g., aqueous solutions having a pH rangingfrom 1 to 7, such as from 3 to 5. In certain embodiments, an acidicsolution may be an acidic by-product of alkali enrichment protocol,e.g., as described above. In some instances, the cation source is aconcentrated hard water that has been produced using a membrane mediatedprotocol, e.g., as described in U.S. Patent Application Ser. No.62/041,568 filed on Aug. 25, 2014; the disclosure of which is hereinincorporated by reference).

A given divalent cation source may be a solid or liquid, as desired. Forexample, a liquid divalent cation source may be employed. Alternatively,a solid divalent cation source, such as a particulate source (e.g., apowder) may be employed.

During the production of solid carbonate compositions from thebicarbonate-containing solution or component thereof (e.g., LCP), onemol of CO₂ may be produced for every 2 mols of bicarbonate ion from thebicarbonate-containing solution or component thereof (e.g., LCP). Forexample, where solid carbonate compositions are produced by addingcalcium cation to the bicarbonate-containing solution or componentthereof (e.g., LCP), the production of solid carbonate compositions,e.g., the form of amorphous calcium carbonate minerals, may proceedaccording to the following reaction:

2HCO₃ ⁻+Ca⁺⁺

CaCO₃·H₂O+CO₂

Ca⁺⁺ _((aq))+2HCO_(3 (aq)) ⁻

CaCO_(3(s))+H₂O_((l))+CO_(2(g))

While the above reaction shows the production of 1 mol of CO₂, 2 molesof CO₂ from the CO₂-containing gas were initially converted tobicarbonate. As such, the overall process sequesters a net 1 mol of CO₂and therefore is an effective CO₂ sequestration process, with a downhillthermodynamic energy profile of −34 kJ mol−1 for the above reaction.

Where carbonate compositions are produced, e.g., as described above,from the CO₂ sequestration protocol, the product carbonate compositionsmay vary greatly. The carbonate product may include one or moredifferent carbonate compounds, such as two or more different carbonatecompounds, e.g., three or more different carbonate compounds, five ormore different carbonate compounds, etc., including non-distinct,amorphous carbonate compounds. Carbonate compounds may be compoundshaving a molecular formulation X_(m)(CO₃)_(n) where X is any element orcombination of elements that can chemically bond with a carbonate groupor its multiple, wherein X is in certain embodiments an alkaline earthmetal and not an alkali metal; wherein m and n are stoichiometricpositive integers. These carbonate compounds may have a molecularformula of X_(m)(CO₃)_(n)·H₂O, where there are one or more structuralwaters in the molecular formula. The amount of carbonate in the product,as determined by coulometry using the protocol described as coulometrictitration, may be 40% or higher, such as 70% or higher, including 80% orhigher.

The carbonate compounds of the precipitated products may include anumber of different cations, such as but not limited to ionic speciesof: calcium, magnesium, sodium, potassium, sulfur, boron, silicon,strontium, and combinations thereof. Of interest are carbonate compoundsof divalent metal cations, such as calcium and magnesium carbonatecompounds. Specific carbonate compounds of interest include, but are notlimited to: calcium carbonate minerals, magnesium carbonate minerals andcalcium magnesium carbonate minerals. Calcium carbonate minerals ofinterest include, but are not limited to: calcite (CaCO₃), aragonite(CaCO₃), vaterite (CaCO₃), ikaite (CaCO₃·6H₂O), and amorphous calciumcarbonate (CaCO₃). Magnesium carbonate minerals of interest include, butare not limited to magnesite (MgCO₃), barringtonite (MgCO₃·2H₂O),nesquehonite (MgCO₃·3H₂O), lanfordite (MgCO₃·5H₂O), hydromagnisite, andamorphous magnesium calcium carbonate (MgCO₃). Calcium magnesiumcarbonate minerals of interest include, but are not limited to dolomite(CaMg)(CO₃)₂), huntite (Mg₃Ca(CO₃)₄) and sergeevite(Ca₂Mg₁₁(CO₃)₁₃·H₂O). The carbonate compounds of the product may includeone or more waters of hydration, or may be anhydrous. In some instances,the amount by weight of magnesium carbonate compounds in the precipitateexceeds the amount by weight of calcium carbonate compounds in theprecipitate. For example, the amount by weight of magnesium carbonatecompounds in the precipitate may exceed the amount by weight calciumcarbonate compounds in the precipitate by 5% or more, such as 10% ormore, 15% or more, 20% or more, 25% or more, 30% or more. In someinstances, the weight ratio of magnesium carbonate compounds to calciumcarbonate compounds in the product ranges from 1.5-5 to 1, such as 2-4to 1 including 2-3 to 1. In some instances, the product product mayinclude hydroxides, such as divalent metal ion hydroxides, e.g., calciumand/or magnesium hydroxides.

Carbonate Precipitation

In some instances, solid carbonate products are produced using aprecipitation protocol, e.g., a protocol which results in the productionof a slurry that includes precipitated carbonate products. Precipitationof solid carbonate compositions from a dissolved inorganic carbon (DIC)composition (e.g., an LCP composition as employed in abicarbonate-mediated sequestration protocol), such as described above,results in the production of a composition that includes bothprecipitated solid carbonate compositions, as well as the remainingliquid from which the precipitated product was produced (i.e., themother liquor). This composition may be present as a slurry of theprecipitate and mother liquor.

The carbonate precipitation conditions may vary, as desired. Forexample, the carbonate precipitation conditions may be transientamorphous calcium carbonate precipitation conditions. In some instances,the carbonate precipitation conditions produce a first precipitatedcarbonate composition and second precipitated carbonate composition. Insuch instances, the first precipitated carbonate composition may be anamorphous calcium carbonate (ACC) and the second precipitated carbonatecomposition is vaterite precursor ACC. In such embodiments, the methodfurther comprises separating the first and second precipitated carbonatecompositions from each other. Conveniently, the first and secondprecipitated carbonate compositions are separated from each other with amembrane. In some instances, the method further includes combining theseparated first and second precipitated carbonate compositions.

This product slurry may be disposed of in some manner following itsproduction. The phrase “disposed of” means that the slurry or a portionthereof, e.g., the solid carbonate composition portion thereof, iseither placed at a storage site or employed for a further use in anotherproduct, i.e., a manufactured or man-made item, where it is “stored” inthat other product at least for the expected lifetime of that otherproduct.

In some instances, this disposal step includes forwarding the slurrycomposition described above to a long-term storage site. The storagesite could be an above ground site, a below ground site or an underwatersite. In these embodiments, following placement of the slurry at thestorage site, the mother liquor component of the slurry may naturallyseparate from the precipitate, e.g., via evaporation, dispersal, etc.

Where desired, the resultant precipitated product (i.e., solid carbonatecomposition) may be separated from the resultant mother liquor.Separation of the solid carbonate composition can be achieved using anyconvenient approach. For example, separation may be achieved by dryingthe solid carbonate composition to produce a dried solid carbonatecomposition. Drying protocols of interest include filtering theprecipitate from the mother liquor to produce a filtrate and thenair-drying the filtrate. Where the filtrate is air dried, air-drying maybe at a temperature ranging from −70 to 120° C., as desired. In someinstances, drying may include placing the slurry at a drying site, suchas a tailings pond, and allowing the liquid component of the precipitateto evaporate and leave behind the desired dried product. Also ofinterest are freeze-drying (i.e., lyophilization) protocols, where thesolid carbonate composition is frozen, the surrounding pressure isreduced and enough heat is added to allow the frozen water in thematerial to sublime directly from the frozen precipitate phase to gas.Yet another drying protocol of interest is spray drying, where theliquid containing the precipitate is dried by feeding it through a hotgas, e.g., where the liquid feed is pumped through an atomizer into amain drying chamber and a hot gas is passed as a co-current orcounter-current to the atomizer direction.

Precipitation of solid carbonate compositions, e.g., as described above,results in the production of a composition that includes bothprecipitated solid carbonate compositions, as well as the remainingliquid from which the precipitated product was produced (i.e., themother liquor). This composition may be present as a slurry of theprecipitate and mother liquor.

The carbonate precipitation conditions may vary, as desired. Forexample, the carbonate precipitation conditions may be transientamorphous calcium carbonate precipitation conditions. In some instances,the carbonate precipitation conditions produce a first precipitatedcarbonate composition and second precipitated carbonate composition. Insuch instances, the first precipitated carbonate composition may be anamorphous calcium carbonate (ACC) and the second precipitated carbonatecomposition is vaterite precursor ACC. In such embodiments, the methodfurther comprises separating the first and second precipitated carbonatecompositions from each other. Conveniently, the first and secondprecipitated carbonate compositions are separated from each other with amembrane. In some instances, the method further includes combining theseparated first and second precipitated carbonate compositions.

Where desired, the method may further include introducing a settingfluid, e.g., a silicate setting solution, into the precipitatedcarbonate composition.

As summarized above, the continuous processes may further includesdewatering the precipitated carbonate composition to produce a solidcarbonate material. The term solid carbonate material refers to avariety of non-liquid formulations, such as paste like, putty like anddry compositions. In some instances, the dewatering includes contactingthe precipitated carbonate composition with a membrane, e.g., anultrafiltration membrane, to produce the solid carbonate material.

In some instances, the method further includes producing unit sizedobjects from the paste, which unit sized objects may be cured, asdesired, e.g., by contacting the objections with a setting solution.

In some instances, the dewatering includes extruding the precipitatedcarbonate composition. In some instances, the extruding includesapplying pressure to remove liquid from the paste. In some instances,the extruding includes applying negative pressure to remove air from thepaste. In some instances, the method further includes introducing one ormore property modulators into the process so that the solid carbonatematerial comprises the property modulator. Property modulators ofinterest may vary, and include but are not limited to reflectancemodulators, pigments, biocides etc.

Where the precipitated product is separated from the mother liquor, theresultant precipitate may be disposed of in a variety of different ways,as further elaborated below. For example, the precipitate may beemployed as a component of a building material, as reviewed in greaterdetail below. Alternatively, the precipitate may be placed at along-term storage site (sometimes referred to in the art as a carbonbank), where the site may be above ground site, a below ground site oran underwater, e.g., deepwater, site.

In certain embodiments, the product carbonate composition is refined(i.e., processed) in some manner prior to subsequent use. Refinement mayinclude a variety of different protocols. In certain embodiments, theproduct is subjected to mechanical refinement, e.g., grinding, in orderto obtain a product with desired physical properties, e.g., particlesize, etc. In certain embodiments, the precipitate is combined with ahydraulic cement, e.g., as a supplemental cementitious material, as asand, a gravel, as an aggregate, etc. In certain embodiments, one ormore components may be added to the precipitate, e.g., where theprecipitate is to be employed as a cement, e.g., one or more additives,sands, aggregates, supplemental cementitious materials, etc. to producefinal product, e.g., concrete or mortar.

In certain embodiments, the carbonate compound is utilized to produceaggregates, e.g., as described in U.S. Pat. No. 7,914,685, thedisclosure of which is herein incorporated by reference. In certainembodiments, the carbonate compound precipitate is employed as acomponent of hydraulic cement. The term “hydraulic cement” is employedin its conventional sense to refer to a composition that sets andhardens after combining with water. Setting and hardening of the productproduced by combination of the cements of the invention with an aqueousfluid result from the production of hydrates that are formed from thecement upon reaction with water, where the hydrates are essentiallyinsoluble in water. Such carbonate compound component hydraulic cements,methods for their manufacture and use include, but are not limited to,those described in U.S. Pat. No. 7,735,274; the disclosure of which isherein incorporated by reference.

Also of interest are dissolution precipitation cements like orthopediccalcium phosphate cements that undergo dissolution into solution andprecipitate out an alternate material. Dissolution precipitation cementsare that are not hydrating however will employ solution as an ion sinkwhich mediates the recrystallization of the lower energy state materialwhich is likened to concrete and can contain volume fillers such asaggregates and finer aggregates.

Also of interest are formed building materials. The formed buildingmaterials of the invention may vary greatly. By “formed” is meantshaped, e.g., molded, cast, cut or otherwise produced, into a man-madestructure defined physical shape, i.e., configuration. Formed buildingmaterials are distinct from amorphous building materials, e.g.,particulate (such as powder) compositions that do not have a defined andstable shape, but instead conform to the container in which they areheld, e.g., a bag or other container. Illustrative formed buildingmaterials include, but are not limited to: bricks; boards; conduits;beams; basins; columns; drywalls etc. Further examples and detailsregarding formed building materials include those described in UnitedStates Published Application No. US20110290156; the disclosure of whichis herein incorporated by reference.

Also of interest are non-cementitious manufactured items that includethe product of the invention as a component. Non-cementitiousmanufactured items of the invention may vary greatly. Bynon-cementitious is meant that the compositions are not hydrauliccements. As such, the compositions are not dried compositions that, whencombined with a setting fluid, such as water, set to produce a stableproduct. Illustrative compositions include, but are not limited to:paper products; polymeric products; lubricants; asphalt products;paints; personal care products, such as cosmetics, toothpastes,deodorants, soaps and shampoos; human ingestible products, includingboth liquids and solids; agricultural products, such as soil amendmentproducts and animal feeds; etc. Further examples and detailsnon-cementitious manufactured items include those described in U.S. Pat.No. 7,829,053; the disclosure of which is herein incorporated byreference.

In some instances, the solid carbonate product may be employed in albedoenhancing applications. Albedo, i.e., reflection coefficient, refers tothe diffuse reflectivity or reflecting power of a surface. It is definedas the ratio of reflected radiation from the surface to incidentradiation upon it. Albedo is a dimensionless fraction, and may beexpressed as a ratio or a percentage. Albedo is measured on a scale fromzero for no reflecting power of a perfectly black surface, to 1 forperfect reflection of a white surface. While albedo depends on thefrequency of the radiation, as used herein Albedo is given withoutreference to a particular wavelength and thus refers to an averageacross the spectrum of visible light, i.e., from about 380 to about 740nm.

As the methods of these embodiments are methods of enhancing albedo of asurface, the methods in some instances result in a magnitude of increasein albedo (as compared to a suitable control, e.g., the albedo of thesame surface not subjected to methods of invention) that is 0.05 orgreater, such as 0.1 or greater, e.g., 0.2 or greater, 0.3 or greater,0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 orgreater, 0.9 or greater, including 0.95 or greater, including up to 1.0.As such, aspects of the subject methods include increasing albedo of asurface to 0.1 or greater, such as 0.2 or greater, e.g., 0.3 or greater,0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 orgreater, 0.9 or greater, 0.95 or greater, including 0.975 or greater andup to approximately 1.0.

Aspects of the methods include associating with a surface of interest anamount of a highly reflective microcrystalline or amorphous materialcomposition effective to enhance the albedo of the surface by a desiredamount, such as the amounts listed above. The material composition maybe associated with the target surface using any convenient protocol. Assuch, the material composition may be associated with the target surfaceby incorporating the material into the material of the object having thesurface to be modified. For example, where the target surface is thesurface of a building material, such as a roof tile or concrete mixture,the material composition may be included in the composition of thematerial so as to be present on the target surface of the object.Alternatively, the material composition may be positioned on at least aportion of the target surface, e.g., by coating the target surface withthe composition. Where the surface is coated with the materialcomposition, the thickness of the resultant coating on the surface mayvary, and in some instances may range from 0.1 mm to 25 mm, such as 2 mmto 20 mm and including 5 mm to 10 mm. Applications in use as highlyreflective pigments in paints and other coatings like photovoltaic solarpanels are also of interest.

The albedo of a variety of surfaces may be enhanced. Surfaces ofinterest include at least partially facing skyward surfaces of bothman-made and naturally occurring objects. Man-made surfaces of interestinclude, but are not limited to: roads, sidewalks, buildings andcomponents thereof, e.g., roofs and components thereof (roof shingles)and sides, runways, and other man-made structures, e.g., walls, dams,monuments, decorative objects, etc. Naturally occurring surfaces ofinterest include, but are not limited to: plant surfaces, e.g., as foundin both forested and non-forested areas, non-vegetated locations, water,e.g., lake, ocean and sea surfaces, etc.

Methods of using the carbonate precipitate compounds described herein invarying applications as described above, including albedo enhancingapplications, as well as compositions produced thereby, are furtherdescribed in U.S. application Ser. Nos. 14/112,495 and 14/214,129; thedisclosures of which applications are herein incorporated by reference.

The resultant mother liquor may also be processed as desired. Forexample, the mother liquor may be returned to the source of thebicarbonated buffer aqueous medium, e.g., ocean, or to another location.

Aspects of the methods optionally include returning the acidicby-product liquid to the place of origin of the aqueous medium that wasused in the first selective membrane processing step. For example, insome embodiments of the methods, the acidic by-product solution isreturned to a naturally occurring or man-made source of aqueous media.Naturally occurring sources of aqueous media include, but are notlimited to, seas, oceans, lakes, swamps, estuaries, lagoons, brines,geological brines, alkaline lakes, inland seas, etc. Man-made sources ofaqueous media include but are not limited to brines produced by waterdesalination plants, waste waters, and the like.

Aspects of the methods optionally include utilizing the acidicby-product solution as a feedwater for various protocols, e.g., fordesalination to produce potable fresh water. Desalination processes thatutilize feedwaters such as the acidic by-product solution include thosedescribed in U.S. Provisional Patent Application No. 61/990,486 and inU.S. Pat. No. 7,744,761, the disclosure of which is herein incorporatedby reference in its entirety.

Non-Slurry Continuous Production Protocols

Instead of precipitation protocols, e.g., as described above, also ofinterest are non-slurry continuous protocols for production of CO₂sequestering materials. As the processes are continuous, they are notbatch processes. In practicing continuous processes of the invention, adivalent cation source, e.g., as described above, is introduced into aflowing aqueous bicarbonate and/or carbonate containing liquid (e.g., abicarbonate rich product containing liquid as described above) underconditions sufficient such that a non-slurry solid phase CO₂sequestering carbonate material is produced in the flowing aqueousbicarbonate rich product.

By “flowing” aqueous liquid is meant a liquid (such as described above)that is moving in or as in a stream, such that it is not stationary. Theflow rate of the liquid, e.g., as determined relative to the site orlocation at which the divalent cations are introduced into the liquid,may vary. In some instances, the flow rate of the liquid ranges from 0.1to 10 m/second, such as 0.2 to 2.0 m/s. In some instances, the flow rateof the liquid ranges from 10 LPD to 40 B LPD (liters per day), such as400,000 LPD to 12 M LPD. In some instances, the liquid is flowingthrough a housing or containment structure, where the length of the flowpath of the liquid may vary. In some instances, the flow path ranges inlength from 0.10 m to 100 m, such as 1 m to 10 m and including 1 m to5.0 m. Along a given flow path, the flow rate of the liquid may beconstant or varied, as desired. For example, the flow rate may be fasterat the site of divalent cation introduction relative to the site of CO₂sequestering carbonate material production. The magnitude of any changein flow rate may vary, where the magnitude of such change, if present,ranges in some instances from 2 to 100 times, such as 5 to 20 times. Theflow rate may be varied using any convenient protocol, e.g., by placingbarriers in the flow path, adjusting the elevation of the flow path,etc.

The amount of divalent cation source that is introduced into the liquidis sufficient to provide for the desired solid phase CO₂ sequesteringcarbonate material. While the amount may vary, in some instances theamount that is introduced into the liquid is sufficient to provide aconcentration of divalent cation in the liquid at a location in the flowpath just before material production that ranges from 10 ppm to 10,000ppm, such as 200 ppm to 2,000 ppm. Where the divalent cation source is aliquid source having a divalent cation concentration ranging from 500ppm to 20,000 ppm, such as 1000 ppm to 5000 ppm, the liquid divalentcation source may be introduced into the flowing liquid at a rateranging from 0.1 m/s to 10 m/s, such as 0.2 m/s to 4 m/s. Alternatively,where the divalent cation source is a dry powder having a divalentcation concentration of 10 to 80% wt/wt., the power divalent cationsource may be introduced into the flowing liquid at a rate ranging from0.2 m/s to 10 m/s, such as 0.2 m/s to 4 m/s.

As the process is a continuous process, upon initiation of the processno solid carbonate material product, apart from any seed structure(e.g., as described below), will be present in the production zone ofthe flow path before introduction of the divalent cations into theflowing liquid. In some embodiments, at a time following the initialintroduction of the divalent cations, a precursor composition forms atlocation downstream from the divalent cation introduction site. Whilethe time between initial introduction and the formation of the non-solidprecursor structure may vary, in some instances the time ranges from0.001 sec to 10 min, such as 0.1 sec to 1 min. In these embodiments, theprecursor composition forms at a distance from the divalent cationintroduction site, where the location may be downstream from thedivalent cation introduction site by a varying distance, where thisdistance may range in some instances from 1 cm to 10 m, such as 2 cm to2 m. The precursor composition may be characterized as a transient zonewhere the initial clusters of carbonate mineral have not yet formed apolytype of the carbonate mineral and are highly unstable, making themmore likely to accrete on to a solid surface than to homogeneouslycrystallize in solution to become part of a slurry.

The zone of accretion (carbonate growth) is defined by saturation indexwhere :

SI=log(IAP/Ksp)

(IAP is the ion activity product over Ksp solubility product) inrelation to the activation energy (Stumm & Morgan 1981) where:

ΔG=16 πσ̂3v̂2/[3(kT Ln S)̂2

where σ is the interfacial energy, v is the molecular volume, k isBoltzmann's constant, T is the absolute temperature, Ln is the naturallogarithm operator, S is the relative supersatruation.

The zone of accretion can furthermore be modified by pressure,temperature and flow rate. Supersaturated solutions between 1× and 1000×supersaturation are of interest, such as 10× and 500× super saturationand including 11× and 300× supersaturation. The zone of accretion may beof a transient nature such that periodic dosing of various divalentcations results in periodicity of saturation index flows through thesystem. Also periodic alkaline component solutions can be introduced tobrine solutions or solutions containing divalent cations creatingsimilar response. Periodicity similar to diurnal cyclic variance seen ingeologic settings where beach rock forms (Ref.

Sedimentary Geology, 33 (1982) 157-172.

The system may be catalyzed by pH modification in the acidic or basicdirection or using any convenient protocol. Introduction of CO₂ orcarbonic acid into the reactor vessel isone modality of acidifying thesystem and modifying the zone of accretion. Another modality is theintroduction of acid, e.g., hydrochloric acid (HCl). In such instances,HCl concentrations between 0.01 and 20%, such as between 0.5 and 10%,including between 1 and 3% may be employed. In some instances, anelectrochemical protocol may be employed to increase the pH of thebicarbonate liquid to produce the concentrated bicarbonate liquid.Electrochemical protocols may vary, and in some instances include thoseemploying an ion exchange membrane and electrodes, e.g., as described inU.S. Pat. Nos. 8,357,270; 7,993,511; 7,875,163; and 7,790,012; thedisclosures of which are herein incorporated by reference. Alkalinitymodulation, e.g., increase or decrease, of the bicarbonate containingliquid may also be accomplished by adding a suitable amount of achemical agent to the bicarbonate containing liquid. Chemical agents foreffecting proton removal generally refer to synthetic chemical agentsthat are produced in large quantities and are commercially available.For example, chemical agents for removing protons include, but are notlimited to, hydroxides, organic bases, super bases, oxides, ammonia, andcarbonates. Hydroxides include chemical species that provide hydroxideanions in solution, including, for example, sodium hydroxide (NaOH),potassium hydroxide (KOH), calcium hydroxide (Ca(OH)₂), or magnesiumhydroxide (Mg(OH)₂). Organic bases are carbon-containing molecules thatare generally nitrogenous bases including primary amines such as methylamine, secondary amines such as diisopropylamine, tertiary such asdiisopropylethylamine, aromatic amines such as aniline, heteroaromaticssuch as pyridine, imidazole, and benzimidazole, and various formsthereof. In some embodiments, an organic base selected from pyridine,methylamine, imidazole, benzimidazole, histidine, and a phophazene isused to remove protons from various species (e.g., carbonic acid,bicarbonate, hydrogen ion, etc.) for precipitation of precipitationmaterial. In some embodiments, ammonia is used to raise pH to a levelsufficient to precipitate precipitation material from a solution ofdivalent cations and an industrial waste stream. Super bases suitablefor use as proton-removing agents include sodium ethoxide, sodium amide(NaNH₂), sodium hydride (NaH), butyl lithium, lithium diisopropylamide,lithium diethylamide, and lithium bis(trimethylsilyl)amide. Oxidesincluding, for example, calcium oxide (CaO), magnesium oxide (MgO),strontium oxide (SrO), beryllium oxide (BeO), and barium oxide (BaO) arealso suitable proton-removing agents that may be used.

Various condition parameters may be modulated during a given method toachieve a desired production of CO₂ sequestering carbonate material. Forexample, pressure may be maintained at a constant level along the flowpath, or pressure may be modulated (i.e., varied) along the flow path,as desired. While the pressure may vary in a given method, in someinstances the pressure ranges from 0.1 atm to 100 atm, such as 1 atm to10 atm. In some embodiments, the pressure is varied, e.g., decreased,along the flow path. The magnitude of any change in pressure may vary,where the magnitude of such change, if present, ranges in some instancesfrom 2 to 100 times, such as 5 to 10 times. The pressure may be variedusing any convenient protocol, e.g., by reducing or increasing thevolume of the flow path at a given location, fluid regime, etc. In someinstances, the pressure is reduced at the location of CO₂ sequesteringcarbonate material relative to the divalent cation introduction site,e.g., where the magnitude of reduction may range from 0% to 100 or more%, such as 10% to 100%.

Alternatively or in addition, the temperature may be maintained at aconstant level along the flow path, or modulated (i.e., varied) alongthe flow path, as desired. While the temperature may vary in a givenmethod, in some instances the temperature ranges from −4° C. to +99° C.,such as 0° C. to 80° C. In some embodiments, the temperature is varied,e.g., decreased or increased, along the flow path. The magnitude of anychange in temperature may vary, where the magnitude of such change, ifpresent, ranges in some instances from 1 to 50° C., such as 2 to 25° C.The temperature may be varied using any convenient protocol, e.g., byheating or cooling the liquid at various location(s) of the flow path.

In some instances, the solid phase CO₂ sequestering carbonate materialis produced at a location that is downstream from the divalent cationsource introduction site. By downstream is meant a location along theflow path in the direction of fluid flow that is separated from thedivalent cation introduction site. The distance between the divalentcation introduction site and the material production site may vary,ranging in some instances from 1 cm to 2.5 km, such as 5 cm to 100 m.

Introduction of the divalent cation source into the flowing aqueousbicarbonate rich product containing liquid as described above results inthe production of a non-slurry solid phase CO₂ sequestering carbonatematerial. By non-slurry solid phase is meant a solid phase that is not aslurry, i.e., if maintained under static conditions it would not be asuspension of small particles in a liquid. As such, upon cessation offlowing liquid through the material production zone, the solid phasematerial produced according to embodiments of the methods settles (i.e.,falls) out of suspension in 10 min or less, such as 5 min or less, andin some instances 1 min or less. As the material is a non-slurry solidphase, in some instances the longest dimension of a given amount of theproduced material is 30 μm or greater, such as 100 μm or greater,including 1000 μm or greater. In some instances the product material isa particulate composition that is made up of a plurality of distinctparticles. In such instances, the plurality of distinct particles mayvary in size, ranging in some instances from 10 to 1,000,000 μm, such as1,000 to 100,000 μm and including 5,000 to 50,000 μm. In suchcompositions, the mean diameter of the particles may vary, and in someinstances ranges from 20 to 20,000 μm, such as 200 to 8,000 μm. Theparticles of such compositions may be regular or irregular, where insome instances the particles are ooids. In these embodiments, thecarbonate material may be produced by successive coating of carbonatecompounds onto growing particles, resulting in production ofparticulates as described above. In some instances, the non-slurry solidphase CO₂ sequestering carbonate material is a lithified unitary object.While the dimensions of such an object may vary, in some instances theobject has a longest dimension ranging from 1,000 to 100,000, such as5,000 to 50,000 μm. In these instances, the lithified object(s) producedin the production zone may be produced by carbonate materials forming inpores or interstices of pre-existing structures, uniting andagglomerating such structures into lithified masses.

The CO₂ sequestering carbonate material produced as described above is afreshwater stable carbonate. By freshwater stable is meant that thecarbonate material is a meta-stable carbonate compound(s) that, uponcombination with fresh water, dissolves and produces a different mineralthat is more stable in fresh water. The solubility of the productmaterial in freshwater may vary, but in some instances has a Ksp of 10⁻⁷or less, such as 10⁻⁶ or less, including 10⁻⁵ or less.

In some instances, the method includes producing the solid phase CO₂sequestering carbonate material in association with a seed structure. Byseed structure is meant a solid structure or material that is presentflowing liquid, e.g., in the material production zone, prior to divalentcation introduction into the liquid. By “in association with” is meantthat the material is produced on at least one of a surface of or in adepression, e.g., a pore, crevice, etc., of the seed structure. In suchinstances, a composite structure of the carbonate material and the seedstructure is produced. In some instances, the product carbonate materialcoats a portion, if not all of, the surface of a seed structure. In someinstances, the product carbonate materials fills in a depression of theseed structure, e.g., a pore, crevice, fissure, etc.

Seed structures may vary widely as desired. The term “seed structure” isused to describe any object upon and/or in which the product carbonatematerial forms. Seed structures may range from singular objects orparticulate compositions, as desired. Where the seed structure is asingular object, it may have a variety of different shapes, which may beregular or irregular, and a variety of different dimensions. Shapes ofinterest include, but are not limited to, rods, meshes, blocks, etc.Also of interest are particulate compositions, e.g., granularcompositions, made up of a plurality of particles. Where the seedstructure is a particulate composition, the dimensions of particles mayvary, ranging in some instances from 0.01 to 1,000,000 μm, such as 0.1to 100,000 μm.

The seed structure may be made up of any convenient material ormaterials. Materials of interest include both carbonate materials, suchas described above, as well as non-carbonate materials. The seedstructures may be naturally occurring, e.g., naturally occurring sands,shell fragments from oyster shells or other carbonate skeletalallochems, gravels, etc., or man-made, such as pulverized rocks, groundblast furnace slag,fly ash, cement kiln dust, red mud, and the like. Forexample, the seed structure may be a granular composition, such as sand,which is coated with the carbonate material during the process, e.g., awhite carbonate material or colored carbonate material, e.g., asdescribed above.

In some instances, seed structure may be coarse aggregates, such asfriable Pleistocene coral rock, e.g., as may be obtained from tropicalareas (e.g., Florida) that are too weak to serve as aggregate forconcrete. In this case the friable coral rock can be used as a seed, andthe solid CO₂ sequestering carbonate mineral may be deposited in theinternal pores, making the coarse aggregate suitable for use inconcrete, allowing it to pass the LA Rattler abrasion test. In someinstances, where a light weight aggregate is desired, the outer surfacewill only be penetrated by the solution of deposition, leaving the innercore relatively ‘hollow’ making a light weight aggregate for use inlight weight concrete.

Methods as described herein may be carried out in a variety of differentcontinuous reactors. Examples of continuous reactors of interest arefurther described below and in the Experimental section. Where acontinuous reactor is employed, the location at which the CO₂sequestering material is produced may be a fluidized bed subunit of thecontinuous reactor. Fluidized bed reactors of interest are configured tomaintain a region of fluidized solids in a continuously flowing medium,and may have a fluid inlet, a fluid outlet, and a region of materialproduction positioned there-between. A given fluidized bed reactor mayhave a single change or multiple chambers, as desired. Where desired,the fluidized bed may include structures, e.g., filters, meshes, frits,etc., or other retaining structures which serve to keep the productmaterial in the fluidize bed.

Methods as described herein may further include separating thenon-slurry solid phase CO₂ sequestering carbonate material from theaqueous bicarbonate rich product containing liquid. Any convenientseparation protocol may be employed to remove the product material fromthe liquid. As such, the product material may be pulled out of theliquid, the liquid may be drained from the product material, etc., asdesired. In some instances, the material is removed from the liquidwhile the liquid is still moving. In yet other instances the material isremoved from the liquid after movement of the liquid has been stopped.Compared with protocols that produce slurry products, the energyassociated with drying the product materials produced according to themethods described herein is much lower. While the magnitude ofdifference in energy usage may vary, in some instances the differenceranges from 2 to 100 times, such as 10 to 50 times per ton of materialproduced. One specific challenge inherent to the field of CO₂sequestering material production is reducing the amount of energyconsumed during the carbonation of CO₂. Common extraneous sources ofenergy use in production methods that produce a CO₂ sequesteringprecipitate material include the removal of water from the precipitatedmaterials after formation. Reducing energy needs normally required toseparate and potentially dry precipitated material form the bulksolution is important. As compared to process in which CO₂ sequesteringprecipitate materials are produced, embodiments of the present methodsproduce dried tons of CO₂ sequestering material using 2 to 100 timesless energy, such as 10 to 50 times less energy, in the waterseparation/drying step.

Continuous processes for producing CO₂ sequestering non-slurrycompositions are further described in U.S. Provisional Application Ser.No. 62/062,084 filed on Oct. 9, 2014, the disclosure of which is hereinincorporated by reference.

Production of Materials from the CO₂ Sequestering Carbonate Products

The product carbonate materials produced, e.g., as described above, maybe further manipulated and/or combined with other compositions toproduce a variety of end-use materials. In certain embodiments, theproduct carbonate composition is refined (i.e., processed) in somemanner. Refinement may include a variety of different protocols. Incertain embodiments, the product is subjected to mechanical refinement,e.g., grinding, in order to obtain a product with desired physicalproperties, e.g., particle size, etc. In certain embodiments, theproduct is combined with a hydraulic cement, e.g., as a sand, a gravel,as an aggregate, etc., e.g., to produce final product, e.g., concrete ormortar.

Also of interest are formed building materials. The formed buildingmaterials of the invention may vary greatly. By “formed” is meantshaped, e.g., molded, cast, cut or otherwise produced, into a man-madestructure defined physical shape, i.e., configuration. Formed buildingmaterials are distinct from amorphous building materials, e.g.,particulate (such as powder) compositions that do not have a defined andstable shape, but instead conform to the container in which they areheld, e.g., a bag or other container. Illustrative formed buildingmaterials include, but are not limited to: bricks; boards; conduits;beams; basins; columns; drywalls etc. Further examples and detailsregarding formed building materials include those described in UnitedStates Published Application No. US20110290156; the disclosure of whichis herein incorporated by reference.

Also of interest are non-cementitious manufactured items that includethe product of the invention as a component. Non-cementitiousmanufactured items of the invention may vary greatly. Bynon-cementitious is meant that the compositions are not hydrauliccements. As such, the compositions are not dried compositions that, whencombined with a setting fluid, such as water, set to produce a stableproduct. Illustrative compositions include, but are not limited to:paper products; polymeric products; lubricants; asphalt products;paints; personal care products, such as cosmetics, toothpastes,deodorants, soaps and shampoos; human ingestible products, includingboth liquids and solids; agricultural products, such as soil amendmentproducts and animal feeds; etc. Further examples and detailsnon-cementitious manufactured items include those described in U.S. Pat.No. 7,829,053; the disclosure of which is herein incorporated byreference.

In some instances, the solid carbonate product may be employed in albedoenhancing applications. Albedo, i.e., reflection coefficient, refers tothe diffuse reflectivity or reflecting power of a surface. It is definedas the ratio of reflected radiation from the surface to incidentradiation upon it. Albedo is a dimensionless fraction, and may beexpressed as a ratio or a percentage. Albedo is measured on a scale fromzero for no reflecting power of a perfectly black surface, to 1 forperfect reflection of a white surface. While albedo depends on thefrequency of the radiation, as used herein Albedo is given withoutreference to a particular wavelength and thus refers to an averageacross the spectrum of visible light, i.e., from about 380 to about 740nm.

As the methods of these embodiments are methods of enhancing albedo of asurface, the methods in some instances result in a magnitude of increasein albedo (as compared to a suitable control, e.g., the albedo of thesame surface not subjected to methods of invention) that is 0.05 orgreater, such as 0.1 or greater, e.g., 0.2 or greater, 0.3 or greater,0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 orgreater, 0.9 or greater, including 0.95 or greater, including up to 1.0.As such, aspects of the subject methods include increasing albedo of asurface to 0.1 or greater, such as 0.2 or greater, e.g., 0.3 or greater,0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 orgreater, 0.9 or greater, 0.95 or greater, including 0.975 or greater andup to approximately 1.0.

Aspects of the methods include associating with a surface of interest anamount of a highly reflective microcrystalline or amorphous materialcomposition effective to enhance the albedo of the surface by a desiredamount, such as the amounts listed above. The material composition maybe associated with the target surface using any convenient protocol. Assuch, the material composition may be associated with the target surfaceby incorporating the material into the material of the object having thesurface to be modified. For example, where the target surface is thesurface of a building material, such as a roof tile or concrete mixture,the material composition may be included in the composition of thematerial so as to be present on the target surface of the object.Alternatively, the material composition may be positioned on at least aportion of the target surface, e.g., by coating the target surface withthe composition. Where the surface is coated with the materialcomposition, the thickness of the resultant coating on the surface mayvary, and in some instances may range from 0.1 mm to 25 mm, such as 2 mmto 20 mm and including 5 mm to 10 mm. Applications in use as highlyreflective pigments in paints and other coatings like photovoltaic solarpanels are also of interest.

The albedo of a variety of surfaces may be enhanced. Surfaces ofinterest include at least partially facing skyward surfaces of bothman-made and naturally occurring objects. Man-made surfaces of interestinclude, but are not limited to: roads, sidewalks, buildings andcomponents thereof, e.g., roofs and components thereof (roof shingles,roofing granules, etc.) and sides, runways, and other man-madestructures, e.g., walls, dams, monuments, decorative objects, etc.Naturally occurring surfaces of interest include, but are not limitedto: plant surfaces, e.g., as found in both forested and non-forestedareas, non-vegetated locations, water, e.g., lake, ocean and seasurfaces, etc.

Methods of using the carbonate precipitate compounds described herein invarying applications as described above, including albedo enhancingapplications, as well as compositions produced thereby, are furtherdescribed in U.S. application Ser. Nos. 14/112,495 and 14/214,129; thedisclosures of which applications are herein incorporated by reference.

Production of Pure CO₂ Gas

As described above, during the production of solid carbonatecompositions from the bicarbonate rich product or component thereof(e.g., LCP), one mol of CO₂ may be produced for every 2 mols ofbicarbonate ion from the bicarbonate rich product or component thereof(e.g., LCP). For example, where solid carbonate compositions areproduced by adding calcium cation to the bicarbonate rich product orcomponent thereof (e.g., LCP), the production of solid carbonatecompositions, e.g., the form of amorphous calcium carbonate minerals,may proceed according to the following reaction:

2HCO₃ ⁻+Ca⁺⁺

CaCO₃·H₂O+CO₂

Ca⁺⁺ _((aq))+2HCO_(3 (aq)) ³¹

CaCO_(3(s))+H₂O_((l))+CO_(2(g))

While the above reaction shows the production of 1 mol of CO₂, 2 molesof CO₂ from the CO₂ containing gas were initially converted tobicarbonate. As such, the overall process sequesters a net 1 mol of CO₂in a carbonate compound and produces 1 mol of substantially pure CO2product gas, which may be sequestered by injection into a subsurfacegeological location, as described in greater detail below. Therefore,the process is an effective CO₂ sequestration process. Contact of thebicarbonate rich product with the cation source results in production ofa substantially pure CO₂ product gas. The phrase “substantially pure”means that the product gas is pure CO₂ or is a CO₂ containing gas thathas a limited amount of other, non-CO₂ components.

Following production of the CO₂ product gas, aspects of the inventionmay include injecting the product CO₂ gas into a subsurface geologicallocation to sequester CO₂. By injecting is meant introducing or placingthe CO₂ product gas into a subsurface geological location. Subsurfacegeological locations may vary, and include both subterranean locationsand deep ocean locations. Subterranean locations of interest include avariety of different underground geological formations, such as fossilfuel reservoirs, e.g., oil fields, gas fields and un-mineable coalseams; saline reservoirs, such as saline formations and saline-filledbasalt formations; deep aquifers; porous geological formations such aspartially or fully depleted oil or gas formations, salt caverns, sulfurcaverns and sulfur domes; etc.

In some instances, the CO₂ product gas may be pressurized prior toinjection into the subsurface geological location. To accomplish suchpressurization the gaseous CO₂ can be compressed in one or more stageswith, where desired, after cooling and condensation of additional water.The modestly pressurized CO₂ can then be further dried, where desired,by conventional methods such as through the use of molecular sieves andpassed to a CO₂ condenser where the CO₂ is cooled and liquefied. The CO₂can then be efficiently pumped with minimum power to a pressurenecessary to deliver the CO₂ to a depth within the geological formationor the ocean depth at which CO₂ injection is desired. Alternatively, theCO₂ can be compressed through a series of stages and discharged as asuper critical fluid at a pressure matching that necessary for injectioninto the geological formation or deep ocean. Where desired, the CO₂ maybe transported, e.g., via pipeline, rail, truck or other suitableprotocol, from the production site to the subsurface geologicalformation.

In some instances, the CO₂ product gas is employed in an enhanced oilrecovery (EOR) protocol. Enhanced Oil Recovery (abbreviated EOR) is ageneric term for techniques for increasing the amount of crude oil thatcan be extracted from an oil field. Enhanced oil recovery is also calledimproved oil recovery or tertiary recovery. In EOR protocols, the CO₂product gas is injected into a subterranean oil deposit or reservoir.

CO₂ gas production and sequestration thereof is further described inU.S. Provisional Application 62/054,322 filed on Sep. 23, 2014, thedisclosure of which is herein incorporated by reference.

Recycling

In some instances, the methods may include recirculating one or more ofthe by-products produced at one or more stages through one or morereactors/stages of the process. Reaction by products that may berecycled into one or more reactors/stages of a given process may vary,and include but are not limited to: saline liquids, pure CO₂, acidicsaline byproducts, bicarbonate rich liquids, etc. Specific examples ofwhere one or more by-products are recycled are reviewed in greaterdetail in the following section.

Specific Embodiments

As described above, methods of the invention may employ an alkalienrichment protocol at one or more different stages of a given CO₂sequestration process. For example, an alkali enrichment protocol may beperformed after and/or before charging a liquid with a gaseous source ofCO₂. FIGS. 11 and 12 illustrate embodiments of methods where a CO₂charged liquid is subjected to an alkali enrichment protocol. In themethod illustrated schematically in FIG. 11, fresh water (i.e., waterhaving a salinity that is at least 2 times lower than the salinity ofsalty water employed in the method) is first contacted with a gaseoussource of CO₂, e.g., as described above, such as flue gas. Contact maybe achieved using any convenient gas/liquid contactor, e.g., a hollowfiber membrane contactor or aqueous froth absorber, such as describedabove. Contact of the fresh water with the gaseous source of CO₂produced a treated CO₂ gas which has been depleted of CO₂ and a CO₂charged product water having DIC, e.g., in the form of carbonate anion(H₂CO₃). In the embodiment illustrated in FIG. 11, the resultant CO₂charged liquid, designated FRESH+H₂CO₃, is that subjected to an alkalienrichment protocol, e.g., as described above, where salty water, e.g.,water having a salinity that is at least 2 times greater than the freshwater employed in the process, is employed as a draw liquid. The alkalienrichment process produces a salty acidic byproduct (e.g., salty wastewater having a low concentration of HCl and a pH ranging from 2 to 3)and an enhanced alkalinity product liquid designated FRESH+NaHCO₃, whichmay be a bicarbonate rich liquid, such as an LCP containing liquid,e.g., as described above. The product liquid is then combined with adivalent cation source (designated Ca²⁺) in a fluidized bed reactor(designed FR) to produce a sequestering carbonate material, CO₂ gas andH₂O. A byproduct of the FR reactor is softened water, which is saltywater with the hardness, e.g., divalent ions (Ca²⁺, Mg²⁺, SO₄ ²⁻, etc.),removed.

As with FIG. 11, FIG. 12 illustrates an embodiment of methods where aCO₂ charged liquid is subjected to an alkali enrichment (i.e., AE)protocol. In the method illustrated schematically in FIG. 12, freshwater (i.e., water having a salinity that is at least 2 times lower thanthe salinity of salty water employed in the method) is first contactedwith a gaseous source of CO₂, e.g., as described above, such as fluegas. Contact may be achieved using any convenient gas/liquid contactor,e.g., a hollow fiber membrane contactor or aqueous froth absorber, suchas described above. Contact of the fresh water with the gaseous sourceof CO₂ produces a treated CO₂ gas which has been depleted of CO₂ and aCO₂ charged product water having DIC, e.g., in the form of carbonateanion (H₂CO₃). In the embodiment illustrated in FIG. 12, the resultantCO₂ charged liquid, designated FRESH+H₂CO₃, is that subjected to analkali enrichment protocol, e.g., as described above, where salty water,e.g., water having a salinity that is at least 2 times greater than thefresh water employed in the process, is employed as a draw liquid. Thealkali enrichment process produces a salty acidic byproduct (e.g., saltywaste water having a low concentration of HCl and a pH ranging from 2 to3) and an enhanced alkalinity product liquid designated FRESH+NaHCO₃,which may be a bicarbonate rich liquid, such as an LCP containingliquid, e.g., as described above. The product liquid is then subjectedto nanofiltration to dewater the liquid, producing potable water andconcentrated bicarbonate rich, e.g., LCP containing, liquid. In theembodiment illustrated in FIG. 12, the resultant concentratedbicarbonate rich liquid is further dried and dewatered to produce solidNaHCO₃.

FIG. 13 illustrates an embodiment of methods where an alkali enrichmentprotocol is employed to produce a CO₂ capture liquid, which liquid isthen contacted with a gaseous source of CO₂ to produce a CO₂ chargedliquid. In the method illustrated schematically in FIG. 13, fresh water(i.e., water having a salinity that is at least 2 times lower than thesalinity of salty water employed in the method) is subjected to analkali enrichment protocol, e.g., as described above, where salty water,e.g., water having a salinity that is at least 2 times greater than thefresh water employed in the process, is employed as a draw liquid. Thealkali enrichment process produces a salty acidic byproduct (e.g., saltywaste water having a low concentration of HCl and a pH ranging from 2 to3) and an enhanced alkalinity product liquid designated FRESH+NaOH,which is then employed as a CO₂ capture liquid. Next, the CO₂ captureliquid is contacted with a gaseous source of CO₂, e.g., as describedabove, such as flue gas. Contact may be achieved using any convenientgas/liquid contactor, e.g., a hollow fiber membrane contactor or aqueousfroth absorber, such as described above. Contact of the CO₂ captureliquid with the gaseous source of CO₂ produces a treated CO₂ gas whichhas been depleted of CO₂ and a CO₂ charged liquid designatedFRESH+NaHCO₃, which may be a bicarbonate rich liquid, such as an LCPcontaining liquid, e.g., as described above. The product liquid is thencombined with a divalent cation source (designated Ca²⁺) in a fluidizedbed reactor (designed FR) to produce a sequestering carbonate material,CO₂ gas and H₂O. A byproduct of the FR reactor is softened water, whichis salty water with the hardness, e.g., divalent ions (Ca²⁺, Mg²⁺, SO₄²⁻, etc.), removed.

As with FIG. 13, FIG. 14 illustrates an embodiment of methods where analkali enrichment protocol is employed to produce a CO₂ capture liquid,which liquid is then contacted with a gaseous source of CO₂ to produce aCO₂ charged liquid. In the method illustrated schematically in FIG. 14,fresh water that includes an amount of sodium bicarbonate, e.g., asproduced by the method illustrated in FIG. 16 (designated FRESH+NaHCO₃),is subjected to an alkali enrichment protocol, e.g., as described above,where salty water, e.g., water having a salinity that is at least 2times greater than the fresh water employed in the process, is employedas a draw liquid. The alkali enrichment process produces a salty acidicbyproduct (e.g., salty waste water having a low concentration of HCl anda pH ranging from 2 to 3) and an enhanced alkalinity product liquiddesignated FRESH+Na₂CO₃, which is then employed as a CO₂ capture liquid.Next, the CO₂ capture liquid is contacted with a gaseous source of CO₂,e.g., as described above, such as flue gas. Contact may be achievedusing any convenient gas/liquid contactor, e.g., a hollow fiber membranecontactor or aqueous froth absorber, such as described above. Contact ofthe CO₂ capture liquid with the gaseous source of CO₂ produces a treatedCO₂ gas which has been depleted of CO₂ and a CO₂ charged liquiddesignated FRESH+NaHCO₃, which may be a bicarbonate rich liquid, such asan LCP containing liquid, e.g., as described above. The product liquidis then combined with a divalent cation source (designated Ca²⁺) in afluidized bed reactor (designed FR) to produce a sequestering carbonatematerial, CO₂ gas and H₂O. A byproduct of the FR reactor is softenedwater, which is salty water with the hardness, e.g., divalent ions(Ca²⁺, Mg²⁺, SO₄ ²⁻, etc.), removed.

FIG. 15 illustrates a method of producing a concentrated divalent cationsource from an initial brine which can be used the methods illustratedin FIGS. 11 to 14. As shown in FIG. 15, an initial brine, e.g., such asdescribed above, is contacted with a nanofiltration membrane (designedNF) to produce a concentrated hard water (designed Ca2+) and softenedwater. FIG. 16 illustrates a method of converted an industrial wastewater (designated reject) into a feed water that may be employed in themethod illustrated in FIG. 14. In FIG. 16, an industrial waste water(designated REJECT, which may be industrial water w/NaHCO₃ present insolution, e.g., seawater RO concentrate) is first contacted with ananofiltration system (designated NF) to produce a hard concentrate byproduct (e.g., concentrate from treatment of REJECT water w/NF,contains, e.g., Ca²⁺, Mg²⁺, SO₄ ²⁻, etc.) and a permeate that containsNaHCO₃. The resultant permeate may be combined with freshwater toproduce a desired feedwater, designated FRESH+NaHCO₃, which feedwatermay then be employed in a process as illustrated in FIG. 14.

FIG. 17 provides a schematic of an embodiment of an alkali enrichmentmediated CO₂ sequestration process which generates alkalinity for CO₂sequestration by converting a bicarbonate solution to acarbonate-containing capture solution which can be further used tocapture CO₂ from flue gas. The resultant, captured CO₂ is then convertedto a CO₂ sequestering calcium carbonate product in the form of coatedsand. This process uses a cation selective membrane and therefore hasbeen given the designation C1 (first cation-selective method). In theprocess illustrated in FIG. 17, the feed stream 1 is a high salinitysolution, containing NaCl, which provides the osmotic pressure to drivealkalinity formation. The stream enters into an Acid/Alkali Recovery(i.e., AR) stack (where the term term “alkali recovery” is equated to“alkali enrichment” as described above) which is loaded with cationselective membranes. The draw stream 2 is a low salinity solutioncontaining bicarbonate ion (sodium bicarbonate). The stream enters theAR stack and is put into contact with a cation-selective membrane whichis also in contact with the feed solution 1. The waste stream derivedfrom the feed solution includes sodium ions that have left the solutionto enter into the draw resulting in a conversion of some NaCl to HCl.The product stream derived from the draw solution has drawn sodium ionsfrom the feed, increasing the solution alkalinity, resulting in theconversion of some bicarbonate to carbonate ion. The generatedalkalinity is used to capture CO₂ (g) when it is brought into contactwith a flue stream (6) in a hollow fiber membrane (e.g., Liqui-cel) CO₂gas contactor. The product stream 5 of stream 4 after it has capturedCO₂ (g) from the flue stream includes generated carbonate ions thatsequester a CO₂ (g) from the flue gas and convert to form 2 bicarbonateions. This bicarbonate-rich solution 5 enters into the fluidized bed toconvert the newly capture CO2 (g) (now in the form of bicarbonate) to acalcium carbonate product. As shown in FIG. 17, stream 6 is aCO₂-containing gas (flue) from which CO₂ must be captured andsequestered, and stream 7 is the waste of stream (6) which has now beenstripped of CO₂ gas. As illustrated, feed stream 6 is selectivelystripped of CO₂, since N₂ gas is still present in the waste stream 7.Product stream 8 is pure CO₂ which results from the reaction ofCaCl₂+2NaHCO₃→CaCO₃ (s)+CO₂ (g)+2NaCl (aq). The amount of CO₂ releasedas pure stream is half of the amount that was sequestered in stream (5).The divalent ion containing stream which induces CaCO₃ formation withinthe fluidized bed with the bicarbonate-rich solution of stream (5) isshown as stream 9. The CaCO₃ formed in the Fluidized bed is of the formof a coating on seed sand particles shown as product stream 10 andstream 11 is the waste stream leaving the fluidized bed contains NaCl.

FIG. 18 is a schematic illustration of a variation of the process shownin FIG. 8 that incorporates stream recycling and therefore has beendesignated C1-R (Recycling). The recycling of streams allows for thereduction of material demand and/or a reduction in capital equipmentrequirements. In FIG. 18, as a portion of the NaCl/HCl waste stream (1)exiting the AR stack is recycled back into the Feed NaCl stream, thenecessary input of new NaCl Feed water and salts may be reduced.Furthermore, since a portion of the product NaHCO₃ stream exiting theLiqui-cel CO₂ contact is recycled back into the Low Salinity NaHCO₃ drawstream entering the AR stack (2), the new NaHCO₃ requirement for thedraw stream is reduced. In fact, if enough is recycled in this fashion,the need for any additional, new NaHCO₃ draw into the AR stack can beeliminated. In this steady state scenario, new NaHCO₃ draw may berequired to initiate the process, but can be regenerated entirely in asustainable fashion. A portion of the product (4), pure CO₂ (g), streamexiting the Fluidized Bed is recycled into the incoming flue gas priorto entering the Liqui-cel CO₂ contactor, which results in a CO₂-enrichedflue gas entering the Liqui-cel CO₂ Contactor, increasing CO₂ uptake.This configuration provides an increase in efficiency of CO₂sequestration until a steady-state situation develops. The NaCl wastestream (5) exiting the Fluidized is partially/totally recycled into theNaCl Feed stream, further reducing salt and water requirements.

FIG. 19 provides a schematic of an embodiment of the methods thatgenerates alkalinity for CO₂ sequestration by converting sequestered CO₂(aq) to a bicarbonate-containing solution that can be used to coatcalcium carbonate product onto sand seeds in the presence of CaCl₂. Theprocess shown in FIG. 19 is an embodiment where alkali enrichment isperformed after CO₂ capture. This process utilizes a cation-selectivemembrane in the AR stack and therefore has been designated C2 (secondcation-selective method). In the embodiment shown in FIG. 19, the liquidstream (1) used to capture CO₂ is a low salinity, “Fresh” solution. Thestream enters into Liqui-cel CO₂ Contactor which sequesters CO₂ fromflue gas (2) in the form of CO₂ (aq). The waste (3) of stream (2) hasbeen stripped of CO₂ but not N₂ gas, and therefore has been selectivelystripped of CO₂ gas. The output of the Liqui-cel contactor is a stream(4) which is a low salinity, “Fresh” solution which now containssequestered CO₂ from flue gas in the form of CO₂ (aq). The draw streamenters the AR stack where the CO₂ (aq) is converted to bicarbonate ion.The stream (4) enters the AR stack and is put into contact with acation-selective membrane that is also in contact with saline solution(6). The bicarbonate-rich product stream (5) exiting the AR stack is alow salinity solution now containing bicarbonate resulting from theincrease in alkalinity due to transfer of sodium ion into the solution.This bicarbonate-rich solution (5) enters into the fluidized bed toconvert the newly capture CO₂ (g) (now in the form of bicarbonate) to acalcium carbonate product (10). As indicated above, stream (6) is a highsalinity feed solution which supplies the sodium ions for alkalinitygeneration in the AR stack, resulting in the conversion of some CO₂ (g)to bicarbonate ion in the product stream (5). The waste stream (7)derived from the AR stack shows that sodium ions have left the solutio,resulting in a conversion of some NaCl to HCl. Stream (8) is thedivalent ion containing stream which induces CaCO₃ formation within thefluidized bed when mixed with the bicarbonate-rich solution of stream(5). As illustrated, the waste stream (9) leaving the fluidized bedcontains NaCl. The CaCO₃ (10) formed in the Fluidized bed is of the formof a coating on seed sand particles. Also shown is a pure CO₂ productstream (11) which results from the reaction of CaCl₂+2NaHCO₃→CaCO₃(s)+CO₂ (g)+2NaCl (aq). The amount of CO₂ released as pure stream ishalf of the amount that was sequestered in stream (5).

The process illustrated in FIG. 20 is analogous to that illustrated inFIG. 19 with the incorporation of stream recycling, and therefore hasbeen designated C2-R (Recycling). The recycling of streams allows forthe reduction of material demand and/or a reduction in capital equipmentrequirements. As shown by stream (1), a portion of the NaCl/HCl wastestream exiting the AR stack is recycled back into the Feed NaCl stream,reducing the necessary input of new NaCl Feed water and salts. The NaClwaste stream (2) exiting the Fluidized bed may be partially/totallyrecycled into the NaCl Feed stream, further reducing salt and waterrequirements. A portion of the pure CO₂ (g) product stream (3) exitingthe Fluidized Bed may be recycled into the incoming flue gas prior toentering the Liqui-cel CO₂ contactor, resulting in a CO₂-enriched fluegas entering the Liqui-cel CO₂ Contactor, increasing CO₂ uptakeefficiency in the contactor. This configuration increases efficiency ofCO₂ sequestration until a steady-state configuration develops.

FIG. 21 provides a schematic of a method embodiment that generatesalkalinity for CO₂ sequestration by converting a bicarbonate solution toa carbonate-containing capture solution which can be further used tocapture CO₂ from flue gas. The resultant, captured CO₂ is then convertedto a calcium carbonate product in the form of coated sand. Thisillustrated method employs an anion-selective membranes in the AR stackand therefore is designated A1 (first, anion-selective). As illustratedin FIG. 21, draw stream (1) is a low salinity solution. The stream (1)enters the AR stack and is put into contact with a anion-selectivemembrane which is also in contact with the feed solution (2). The feedstream (2) is a high salinity solution, containing NaCl and sodiumbicarbonate, which provides the osmotic pressure to drive alkalinityformation. The stream (2) enters into an Acid/Alkali Recovery (AR) stackwhich loaded with anion selective membranes. Stream (3) is the wastestream that is derived from the draw solution. Chloride ions have leftthe feed solution to enter into the draw resulting in the formation ofHCl (aq) in the waste stream (3). The product stream (4) derived fromthe feed solution is a enhanced alkalinity solution. The solution hastransferred chloride ions to the draw, increasing the solutionalkalinity, resulting in the conversion of some bicarbonate to carbonateion. The generated alkalinity is used to capture CO₂ (g) when it isbrought into contact with a flue stream (6) in a Liqui-cell CO₂contactor. Stream (5) is the product stream of stream (4) after it hascaptured CO₂ (g) from the flue stream. The generated carbonate ions instream (4) sequester a CO₂ (g) from the flue gas and convert to form 2bicarbonate ions. This bicarbonate-rich solution enters into thefluidized bed to convert the newly capture CO₂ (g) (now in the form ofbicarbonate) to a calcium carbonate product. Stream (6) is aCO₂-containing gas (flue) from which CO₂ must be captured andsequestered, while stream (7) is the waste of stream (6) which has nowbeen stripped of CO₂ gas. Stream (8) is a pure CO₂ product stream whichresults from the reaction of CaCl2+2NaHCO₃→CaCO₃ (s)+CO₂ (g)+2NaCl (aq).The amount of CO₂ released as pure stream is half of the amount that wassequestered in stream (5). The divalent ion containing stream (9)induces CaCO₃ formation within the fluidized bed with thebicarbonate-rich solution of stream (5). The CaCO₃ (10) formed in theFluidized bed is of the form of a coating on seed sand particles. Stream(11) is the waste stream leaving the fluidized bed contains NaCl.

FIG. 22 provides a schematic of a process analogous to that shown inFIG. 21 with the incorporation of stream recycling, and therefore hasbeen designated A1-R (Recycled). The recycling of streams allows for thereduction of material demand and/or a reduction in capital equipmentrequirements. As shown in FIG. 22, a portion of the HCl waste stream (1)exiting the AR stack is recycled back into the draw “Fresh” stream, suchthat the necessary input of new “Fresh” draw stream water is reduced. Asillustrated by stream (2), a portion of the product NaHCO₃ streamexiting the Liqui-cel CO₂ contact is recycled back into the highsalinity NaHCO₃ feed stream entering the AR stack, such that additionalNaHCO₃ requirements for the draw stream is reduced. In some instances,if enough is recycled in this fashion, the need for any additional, newNaHCO₃ draw into the AR stack can be eliminated. In this steady stateconfiguration, new NaHCO₃ draw may be required to initiate the process,but can be regenerated entirely in a sustainable fashion. As shown bystream (3), the NaCl waste stream exiting the Fluidized bed ispartially/totally recycled into the NaCl Feed stream, further reducingsalt and water requirements. As shown by stream (4), a portion of theproduct, pure CO₂ (g), stream exiting the Fluidized Bed is recycled intothe incoming flue gas prior to entering the Liqui-cel CO₂ contactor.This configuration produces a CO₂-enriched flue gas entering theLiqui-cel CO₂ Contactor, increasing CO₂ uptake. This approach increasesefficiency of CO₂ sequestration until a steady-state configurationdevelops.

FIG. 23 provides a schematic illustration of method that generatesalkalinity for CO₂ sequestration by converting sequestered CO₂ (aq) to abicarbonate-containing solution that can be used to coat calciumcarbonate product onto sand seeds in the presence of CaCl₂. This processutilizes an anion-selective membrane in the AR stack and therefore hasbeen designated A2 (second anion-selective method). As shown in FIG. 23,the feed stream (1) is a high salinity solution containing sodiumchloride. The stream enters into Liqui-cel CO₂ Contactor whichsequesters CO₂ from flue gas (2) in the form of CO₂ (aq). The waste (3)of stream (2) has been stripped of CO₂ gas. The feed stream (4) is ahigh salinity, NaCl (aq) solution which now contains sequestered CO₂from flue gas in the form of CO₂ (aq). The feed stream (4) enters the ARstack where the CO₂ (aq) will be converted to bicarbonate ion. Thestream enters the AR stack and is put into contact with ananion-selective membrane which is also in contact with the draw solution(6). The bicarbonate-rich product stream (5) exiting the AR stack is ahigh salinity solution now containing bicarbonate resulting from theincrease in alkalinity due to transfer of chloride ion into thesolution. This bicarbonate-rich solution (5) enters into the fluidizedbed to convert the newly capture CO₂ (g) (now in the form ofbicarbonate) to a calcium carbonate product. The low salinity drawsolution (6) which draws HCl ions for alkalinity generation in the ARstack results in the conversion of some CO₂ (g) to bicarbonate ion inthe product stream (5) and the production of waste stream (7) thatincludes chloride ions which have left the feed solution to enter intothe draw resulting in the generation of alkalinity in the feed. Stream(8) is the divalent ion containing stream which induces CaCO₃ formationwithin the fluidized bed when mixed with the bicarbonate-rich solutionof stream (5), and stream (9) is the CaCO₃ formed in the Fluidized bedin of the form of a coating on seed sand particles. The waste stream(10) leaving the fluidized bed contains NaCl. Stream (11) is a pure CO₂product stream which results from the reaction of CaCl₂+2NaHCO₃→CaCO₃(s)+CO₂ (g)+2NaCl (aq). The amount of CO₂ released as pure stream ishalf of the amount that was sequestered in stream (5).

FIG. 24 provides a schematic of a process analogous to that shown inFIG. 23 with the incorporation of stream recycling, and therefore hasbeen designated A2-R (Recycled). The recycling of streams allow for thereduction of material demand and/or a reduction in capital equipmentrequirements. As illustrated by stream (1), the NaCl waste streamexiting the Fluidized bed is partially/totally recycled into the NaClFeed stream, reducing salt and water requirements. In stream (2), aportion of the pure CO₂ (g) product stream exiting the Fluidized Bed isrecycled into the incoming flue gas prior to entering the Liqui-cel CO₂contactor, which results in a CO₂-enriched flue gas entering theLiqui-cel CO₂ contactor, increasing CO₂ uptake efficiency in thecontactor. This approach increases efficiency of CO₂ sequestration untila steady-state configuration develops. As shown in stream (3), a portionof the HCl waste stream exiting the AR stack is recycled back into thedraw “Fresh” water stream entering the AR stack, such that the necessaryinput of new draw water is reduced.

FIGS. 25 to 27 provides illustrations of different embodiments ofmembrane mediated processes in which an alkali enrichment protocol isemployed to produce a CO₂ capture liquid, and the CO₂ sequestrationprocess is one that produces a CO₂ sequestering carbonate precipitate,which precipitate may then be further manipulated, e.g., to produce avariety of products. As illustrated in these protocols there aremultiple membrane modules in the processes, where each module may beaccomplished by a single membrane device or a plurality of membranedevices, e.g., arranged in parallel or in series, as desired.

In FIG. 25, a water source is first subjected to an alkali enrichmentprotocol in membrane module B. In membrane module B, with, e.g.,seawater, brine water, wastewater from a seawater desalination plant,produced water, etc., osmotic pressure is employed as the driving forceto bring about a pH gradient between a feed solution and a drawsolution. If, for example, the draw solution is NaCl and the feedsolution is H₂O, the reverse salt flux permeates NaOH or HCl back to thefeed solution. The product CO₂ absorbing solution is the one, eitherfeed or draw, that has more NaOH and therefore a higher, more alkalinepH. This AE membrane module may vary as described above, and in someinstances is a forward osmosis membrane module. In FIG. 25, an initialgaseous source of CO₂, e.g., flue gas, is first processed in membranemodule A, which may include a gas separation membrane configured toseparate gaseous components of a non-treated flue gas input streamcontaining, e.g., <1-20% (v/v) CO₂, so that the treated flue gas outputstream contains, e.g., 30-90% (v/v) CO₂. As shown in FIG. 25, thetreated flue gas and product CO₂ capture liquid are then combined inmodule D, which is a hollow fiber membrane device, e.g., as describedabove. The pressures in module D may vary, ranging from, e.g., 1-<1,000psi, so as to combine CO₂ absorbing solution with treated flue gashaving, e.g., 30-90% (v/v) CO₂. The liquid and gas are combined in amembrane contactor that maximizes the gas-liquid interface, allowing forefficient, rapid absorption and dissolution of gaseous CO₂, and thusproviding an exit solution that contains LCP droplets. The LCPcontaining exit solution is then conveyed to module F, which contains amembrane configured to dewater the product solution and concentrate theLCP droplets. As reviewed above, the membrane of this module may vary,where specific types of membranes that may be employed in this moduleinclude reverse osmosis membranes, nanofiltration membranesultrafiltration membranes. In module F, with a feed solution containingLCP droplets, hydraulic pressure may be employed in the range of, e.g.,1-<1,000 psi, as the driving force to physically separate andconcentrate the LCP droplets from the bulk solution. If, for example,the feed solution is 15 ppm in carbon, it is dewatered to an extent thatthe solution is 750 ppm in carbon, a 50-fold increase in concentration.In the process of FIG. 25, the permeate of module F is then conveyed tomodule H, which is configured so that with a feed solution containing,e.g., dissolved mono-, di- and trivalent ions such as but not limited toNa⁺, K⁺, or, HCO₃ ⁻, Ca²⁺, Mg²⁺, Sr²⁺, Hg²⁺, SO₄ ²⁻, CO₃ ²⁻, Al³⁺, PO₄³⁻, hydraulic pressures in the range of, e.g., 1-<1,000 psi, may beemployed as the driving force to physically remove ions from solution,so as to pass pure H₂O to the permeate. The specific type of membrane inthis module may vary, wherein membranes of interest include reverseosmosis and nanofiltration membranes. Concentrated LCP containing liquidproduced with module F is conveyed to a mixing tank where it is combinedwith a source of divalent cations under conditions sufficient to producea calcium carbonate precipitate and pure CO₂ gas. While the divalentcation source that is combined with the concentrated LCP liquid in themixing tank may vary, in the illustrated embodiment the devalent cationsource is one that has been produced from an initial brine by a membranemediated concentration membrane module G. In membrane module G, with aninitial brine feed solution containing, e.g., alkaline earth metals(Group II on the Periodic Table), hydraulic pressures in the range of,e.g., 1-<1,000 psi are employed as the driving force to physicallyseparate and concentrate the alkaline earth metal ions from the bulksolution. If, for example, e.g., a feed solution is 400 ppm in calcium,it is dewatered to an extent that the solution is 40,000 ppm in calcium,100-fold increase in concentration. While the membranes employed in suchmodules may vary, membranes of interest include reverse osmosismembranes, nanofiltration membranes ultrafiltration membranes. Thepermeate of module G may be further processed in another membrane module(e.g., such as described above) to produce a salt water waste produceand a bicarbonate rich medium (identified as CarbonMix™). As shown inFIG. 25, the precipitated product produced in the mixing tank isconveyed to module J, which is employed to mechanically dewater theprecipitated product. In module J, with a feed solution containing asuspension, slurry, sludge, paste, etc., of, e.g., alkaline earth metalcarbonates (such as but not limited to CaCO₃, MgCO₃, SrCO₃, BaCO₃,HgCO₃) and other solid materials (such as but not limited to SiO₂,Al₂O₃, Fe₂O₃) formed from mixing, blending, combining, etc., solutionsof concentrated LCP droplets and concentrated alkaline earth metals,hydraulic pressures in the range of, e.g., 1-<1,000 psi, are employed asthe driving force to physically dewater the suspension, slurry, sludge,paste, etc., to the extent that the isolated suspension, slurry, sludge,paste, etc., contains between 10-50% water by mass. While the membranesemployed in this module may vary, membranes of interest includeultrafiltration and microfiltration membranes. The resultant dewateredproduct may then be conveyed to an extruder, which is configured toproduce solid carbonate pellets from the dewatered product, e.g., asdescribed above.

FIG. 26 provides a view of a protocol in which hydraulic pressure isemployed as a driving force to produce a CO₂ capture liquid with analkali enrichment module. In FIG. 26, a water source is first subjectedto an alkali enrichment protocol in membrane module C. In membranemodule C, with, e.g., seawater, brine water, pond water at a powerplant, wastewater from rinsing a ready-mix concrete truck, producedwater, etc., use hydraulic pressure as the driving force to bring abouta pH gradient between the permeate solution and the concentratesolution. If, for example, the feed solution contains NaCl and H₂O, theapplied pressure will drive NaOH and HCl to separate across themembrane. The CO₂ absorbing solution is the one, either permeate orconcentrate, that has more NaOH and therefore a higher, more alkalinepH. Another example might be a feed solution that contains NaHCO₃whereby the applied pressure will drive the following reaction: 2NaHCO₃=Na₂CO₃+H₂CO₃. The CO₂ absorbing solution is the one, eitherpermeate or concentrate, that has more Na₂CO₃ and therefore a higher,more alkaline pH. As shown in FIG. 26, the resultant CO₂ absorbingsolution (i.e., CO₂ capture liquid) is conveyed to membrane module Ewhere it is combined with an untreated gaseous source of CO₂, e.g., fluegas. In membrane module E, at pressures ranging from, e.g., 1-<1,000psi, CO₂ absorbing solution is combined with non-treated flue gashaving, e.g., <1 -20% (v/v) CO₂. The liquid and gas are combined in amembrane contactor, e.g., a hollow fiber membrane containing device suchas described above, that maximizes the gas-liquid interface, allowingfor efficient, rapid absorption and dissolution of gaseous CO₂, and thusproviding an exit solution that contains LCP droplets. Other gases fromthe non-treated flue gas input stream, e.g., N₂, are not absorbed by theCO₂ absorbing solution, but are passed out of the contactor. The LCPcontaining exit solution is then conveyed to module F, which contains amembrane configured to dewater the product solution and concentrate theLCP droplets. As reviewed above, the membrane of this module may vary,where specific types of membranes that may be employed in this moduleinclude reverse osmosis membranes, nanofiltration membranesultrafiltration membranes. In module F, with a feed solution containingLCP droplets, hydraulic pressure may be employed in the range of, e.g.,1-<1,000 psi, as the driving force to physically separate andconcentrate the LCP droplets from the bulk solution. If, for example,the feed solution is 15 ppm in carbon, it is dewatered to an extent thatthe solution is 750 ppm in carbon, a 50-fold increase in concentration.In the process of FIG. 26, the permeate of module F is then conveyed tomodule H, which is configured so that with a feed solution containing,e.g., dissolved mono-, di- and trivalent ions such as but not limited toNa⁺, K⁺, Cl⁻, HCO₃ ⁻, Ca²⁺, Mg²⁺, Sr²⁺, Hg²⁺, SO₄ ²⁻, CO₃ ²⁻, Al³⁺, PO₄³⁻, hydraulic pressures in the range of, e.g., 1-<1,000 psi, may beemployed as the driving force to physically remove ions from solution,so as to pass pure H₂O to the permeate. The specific type of membrane inthis module may vary, wherein membranes of interest include reverseosmosis and nanofiltration membranes. Concentrated LCP containing liquidproduced with module F is conveyed to membrane module J, where it iscombined with a source of divalent cations. While the divalent cationsource that is combined with the concentrated LCP liquid in the mixingtank may vary, in the illustrated embodiment the devalent cation sourceis one that has been produced from a brine by a membrane mediatedconcentration membrane module G. In membrane module G, with an initialbrine feed solution containing, e.g., alkaline earth metals (Group II onthe Periodic Table), hydraulic pressures in the range of, e.g., 1-<1,000psi are employed as the driving force to physically separate andconcentrate the alkaline earth metal ions from the bulk solution. If,for example, e.g., a feed solution is 400 ppm in calcium, it isdewatered to an extent that the solution is 40,000 ppm in calcium,100-fold increase in concentration. While the membranes employed in suchmodules may vary, membranes of interest include reverse osmosismembranes, nanofiltration membranes ultrafiltration membranes. The brinethat is concentrated in module G in the protocol illustrated in FIG. 26is one that has been initial produced from seawater using membranemodule I. In membrane module I, with a feed solution containing, e.g.,dissolved mono-, di- and trivalent ions such as but not limited to Na⁺,K⁺, Cl⁻, HCO₃ ⁻, Ca²⁺, Mg²⁺, Sr²⁺, Hg²⁺, SO₄ ²⁻, CO₃ ²⁻, Al³⁺, PO₄ ³⁻,hydraulic pressures in the range of, e.g., 1-<1,000 psi, are employed asthe driving force to physically remove the di- and trivalent ions fromsolution, such as but not limited to Ca²⁺, Mg²⁺, Sr²⁺, Hg²⁺, SO₄ ²⁻, CO₃²⁻, Al³⁺, PO₄ ³⁻, so as to pass solutions with monovalent ions to thepermeate, such as but not limited to Na⁺, K⁺, Cl⁻, HCO₃ ⁻, thussoftening the water. While the membranes employed in such modules mayvary, membranes of interest include reverse osmosis membranes,nanofiltration membranes ultrafiltration membranes. As shown in FIG. 26,combination of the divalent cation source and LCP containing liquid inmodule J produces a precipitated product, which is then mechanicallydewatered. In module J, the resultant suspension, slurry, sludge, paste,etc., of, e.g., alkaline earth metal carbonates (such as but not limitedto CaCO₃, MgCO₃, SrCO₃, BaCO₃, HgCO₃) and other solid materials (such asbut not limited to SiO₂, Al₂O₃, Fe₂O₃) formed from mixing, blending,combining, etc., solutions of concentrated LCP droplets and concentratedalkaline earth metals, hydraulic pressures in the range of, e.g.,1-<1,000 psi, are employed as the driving force to physically dewaterthe suspension, slurry, sludge, paste, etc., to the extent that theisolated suspension, slurry, sludge, paste, etc., contains between10-50% water by mass. While the membranes employed in this module mayvary, membranes of interest include ultrafiltration and microfiltrationmembranes. The resultant dewatered product may then be conveyed to anextruder, which is configured to produce solid carbonate pellets fromthe dewatered product, e.g., as described above. In the process shown inFIG. 26, pure CO₂ produced by the precipitation reaction is recycled toenrich the gaseous source of CO₂ which enter membrane module G.

FIG. 27 illustrates a process in which seawater is employed as aninitial source water and is processed with an alkali enrichment protocolto produce a CO₂ capture liquid. In FIG. 27, seawater is first processedat membrane module H, which is configured so that with a seawater feedsolution containing, e.g., dissolved mono-, di- and trivalent ions suchas but not limited to Na⁺, K⁺, Cl⁻, HCO₃ ⁻, Ca²⁺, Mg²⁺, Sr²⁺, Hg²⁺, SO₄²⁻, CO₃ ²⁻, Al³⁺, PO₄ ³⁻, hydraulic pressures in the range of, e.g.,1-<1,000 psi, may be employed as the driving force to physically removeions from solution, so as to pass pure H₂O to the permeate. The specifictype of membrane in this module may vary, wherein membranes of interestinclude reverse osmosis and nanofiltration membranes. The retentatesolution is then conveyed to membrane module B. In membrane module B,with, e.g., seawater, brine water, wastewater from a seawaterdesalination plant, produced water, etc., osmotic pressure is employedas the driving force to bring about a pH gradient between a feedsolution and a draw solution. If, for example, the draw solution is NaCland the feed solution is H₂O, the reverse salt flux permeates NaOH orHCl back to the feed solution. The product CO₂ absorbing solution is theone, either feed or draw, that has more NaOH and therefore a higher,more alkaline pH. This AR membrane module may vary as described above,and in some instances is a forward osmosis membrane module. As shown inFIG. 27, the resultant CO₂ absorbing solution (i.e., CO₂ capture liquid)is conveyed to membrane module E where it is combined with an untreatedgaseous source of CO₂, e.g., flue gas. In membrane module E, atpressures ranging from, e.g., 1-<1,000 psi, CO₂ absorbing solution iscombined with non-treated flue gas having, e.g., <1-20% (v/v) CO₂. Theliquid and gas are combined in a membrane contactor, e.g., a hollowfiber membrane containing device such as described above, that maximizesthe gas-liquid interface, allowing for efficient, rapid absorption anddissolution of gaseous CO₂, and thus providing an exit solution thatcontains LCP droplets. Other gases from the non-treated flue gas inputstream, e.g., N₂, are not absorbed by the CO₂ absorbing solution, butare passed out of the contactor. The LCP containing exit solution isthen conveyed to module F, which contains a membrane configured todewater the product solution and concentrate the LCP droplets. Asreviewed above, the membrane of this module may vary, where specifictypes of membranes that may be employed in this module include reverseosmosis membranes, nanofiltration membranes ultrafiltration membranes.In module F, with a feed solution containing LCP droplets, hydraulicpressure may be employed in the range of, e.g., 1-<1,000 psi, as thedriving force to physically separate and concentrate the LCP dropletsfrom the bulk solution. If, for example, the feed solution is 15 ppm incarbon, it is dewatered to an extent that the solution is 750 ppm incarbon, a 50-fold increase in concentration. In the process of FIG. 27,the permeate of module F is then conveyed to a first module H, which isconfigured so that with a feed solution containing, e.g., dissolvedmono-, di- and trivalent ions such as but not limited to Na⁺, K⁺, Cl⁻,HCO₃ ⁻, Ca²⁺, Mg²⁺, Sr²⁺, Hg²⁺, SO₄ ²⁻, CO₃ ²⁻, Al³⁺, PO₄ ³⁻, hydraulicpressures in the range of, e.g., 1-<1,000 psi, may be employed as thedriving force to physically remove ions from solution, so as to passpure H₂O to the permeate. The specific type of membrane in this modulemay vary, wherein membranes of interest include reverse osmosis andnanofiltration membranes. Concentrated LCP containing liquid producedwith module F is conveyed to a second module H, where it is combinedwith a source of divalent cations to produce produce pure water and aprecipitate containing liquid. The resultant precipitated productproduced by module H is conveyed to module J, which is employed tomechanically dewater the precipitated product. In module J, with a feedsolution containing a suspension, slurry, sludge, paste, etc., of, e.g.,alkaline earth metal carbonates (such as but not limited to CaCO₃,MgCO₃, SrCO₃, BaCO₃, HgCO₃) and other solid materials (such as but notlimited to SiO₂, Al₂O₃, Fe₂O₃) formed from mixing, blending, combining,etc., solutions of concentrated LCP droplets and concentrated alkalineearth metals, hydraulic pressures in the range of, e.g., 1-<1,000 psi,are employed as the driving force to physically dewater the suspension,slurry, sludge, paste, etc., to the extent that the isolated suspension,slurry, sludge, paste, etc., contains between 10-50% water by mass.While the membranes employed in this module may vary, membranes ofinterest include ultrafiltration and microfiltration membranes. Theresultant dewatered product may then be conveyed to a spray dryer, whichis configured to produce solid carbonate powder from the dewateredproduct, e.g., as described above.

Additional Aspects

Where desired, a given CO₂ sequestration process as described herein mayinclude a number of additional characteristics, e.g., as describedbelow.

Operating Pressure in Multiple Membrane Module Embodiments

As described above, in some instances the process employs multiplemembrane modules, which modules may be employed in the process toachieve a variety of different results, e.g., alkali enrichment, CO₂absorption, LCP dewatering/concentration, production of divalent cationsources, precipitate dewatering, byproduct processing, etc. In someinstances where multiple membrane modules are employed, two or more ofthe modules, including three or more of the modules, such as four ormore of the modules, e.g., five or more of the modules, up to andincluding all of the modules, may be operated a the substantially thesame, if the same pressure. In such instances, among any two modulesbeing operated at substantially the same pressure, the magnitude of anydifference in pressure will be small, being in some instances 5 atm orless, such as 4 atm or less, e.g., 3 atm or less, including 2 atm orless, such as 1 atm or less, e.g., 0.5 atm or less. In some instances,such systems may further include an energy recovery module, e.g., anenergy recovery piston.

Multiple Functional Modules

A given CO₂ sequestration process may be characterized by having asingle type of each functional module or multiple copies of one or moreof a given functional module of the process. For example, a givenprocess may include a single alkali enrichment module or two more alkalidistinct alkali enrichment modules. Similarly, a given process mayinclude a single CO₂ liquid charging module or two more CO₂ liquidcharging modules. Where multiple copies of a given functional module areemployed, the modules may be arranged in parallel or series, as desired.An example of a method having multiple copies of alkali enrichment andCO₂ liquid charging modules arranged in series is illustrated in FIG.28.

Low Parasitic Load

Embodiments of the subject methods may be viewed as a low parasitic loadprocesses. By low parasitic load processes is meant that, when theprocesses are employed to sequester CO₂ from a CO₂ generating powersource, the parasitic load placed on the CO₂ generating power source tosequester CO₂ is minimal. As the methods of such embodiments are lowparasitic load methods, any parasitic load placed on the power source isminimal, wherein in some instances, the parasitic load is 20% or less,such as 11% or less, including 7% or less.

Continuous Process

While the subject methods may be performed in a continuous or batchmanner, in some instances aspects of the invention include continuousprocesses to produce solid CO₂ sequestering carbonate materials, e.g.,as described above. As the processes of such embodiments are continuous,they are not batch processes. In practicing continuous processes of theinvention, the process time (i.e., the time from input of water into theprocess to the time of production of a final CO₂ sequestering productmay vary, and in some instances ranges from 5 minutes to 50 hours, suchas 5 minutes to 25 hours, e.g., 5 minutes to 5 hours.

UTILITY

Methods as described herein find use in CO₂ sequestration applications.As reviewed above, by “CO₂ sequestration” is meant the removal orsegregation of an amount of CO₂ from an environment, such as the Earth'satmosphere or a gaseous waste stream produced by an industrial plant, sothat some or all of the CO₂ is no longer present in the environment fromwhich it has been removed. CO₂ sequestering methods of the inventionsequester CO₂, producing a storage stable carbon dioxide sequesteringproduct from an amount of CO₂ such that the CO₂ from which the productis produced is then sequestered in that product. The storage stable CO₂sequestering product is a storage stable composition that incorporatesan amount of CO₂ into a storage stable form, such as an above-groundstorage or underwater storage stable form, so that the CO₂ is no longerpresent as, or available to be, a gas in the atmosphere. Depending onthe particular embodiment, the storage stable form may be a liquid or asolid. Sequestering of CO₂ according to methods of the invention resultsin prevention of CO₂ gas from entering the atmosphere and allows forlong-term storage of CO₂ in a manner such that CO₂ does not become partof the atmosphere.

SYSTEMS

Aspects of the invention include systems which are configured forpracticing the methods, e.g., as described above. A system is anapparatus that includes functional modules or reactors, e.g., asdescribed above, that are operatively coupled in a manner sufficient toperform methods of the invention, e.g., as described above. In someembodiments, a system includes one or more alkali enrichment modulesconfigured or adapted to produce one or more of the liquids describedabove, e.g., a product liquid of enhanced alkalinity. In someembodiments, a system includes one or more membrane mediated alkalienrichment modules, e.g., as described above. In some embodiments, asystem includes a CO₂ gas/liquid contactor module, which is configuredfor contacting a CO₂ containing gas with a liquid, e.g., as describedabove. In some embodiments, the system includes one or more carbonateproduction modules, e.g., as described above. Additional detailsregarding systems and modules of interest may be found in U.S. patentapplication Ser. No. 14/112,495; the disclosure of which is hereinincorporated by reference. In some instances, the systems and modulesthereof are industrial scale systems, by which is meant that they areconfigured to process industrial scale amounts/volumes of inputcompositions (e.g., gases, liquids, etc.). For example, the systems andmodules thereof, e.g., alkali enrichment modules, CO₂ contactor modules,etc., are configured to process industrial scale volumes of liquids,e.g., 1,000 gal/day or more, such as 10,000 gal/day or more, including25,000 gal/day or more, where in some instances, the systems and modulesthereof are configured to process 1,000,000,000 gal/day or less, such as500,000,000 gal/day or less (Jake-please confirm these values make senseas potential upper limits). Similarly, the systems and modules thereof,e.g., CO₂ contactor modules, etc., are configured to process industrialscale volumes of gases, e.g., 25,000 cubic feet/hour or more, such as100,000 cubic feet/hour or more, including 250,000 cubic feet/hour ormore, where in some instances, the systems and modules thereof areconfigured to process 500,000,000 cubic feet/hour or less, such as100,000,000 cubic feet/hour or less.

In some embodiments, a system is in fluidic communication with a sourceof aqueous media, such as a naturally occurring or man-made source ofaqueous media, and may be co-located with a location where a CO₂sequestration protocol is conducted. The systems may be present on landor sea. For example, a system may be a land based system that is in acoastal region, e.g., close to a source of sea water, or even aninterior location, where water is piped into the system from a saltwater source, e.g., an ocean. Alternatively, a system may be a waterbased system, i.e., a system that is present on or in water. Such asystem may be present on a boat, ocean-based platform etc., as desired.In certain embodiments, a system may be co-located with an industrialplant, e.g., a power plant, at any convenient location.

The following examples are offered by way of illustration and not by wayof limitation.

EXPERIMENTAL

Alkalinity was transferred from a draw liquid to feedwater as follows. Aflatplate analyzer which tested the alkalinity generation in the Feedstream by means of a Nafion membrane (e.g., as described in Okada etal., Electrochimica Acta (1998) 43: 3741-3747), was employed. The setupused a 2M NaCl solution for the draw stream and a pure, deionized waterfor the feedwater stream. The pressure was 5 feet of pressure for eachsolution. The feed stream increased in pH from pH 5.4 to pH 7.8 due tothe preferential migration of Na⁺ ion across the membrane over the Cl⁻ion. This results in net NaOH in the feed stream that can be used tomake a basic, CO₂ capture solution with high alkalinity. Theexperimental set up and results are further illustrated in FIG. 7.

Notwithstanding the appended clauses, the disclosure is also defined bythe following clauses, which clauses are further described in U.S.Provisional Application Ser. No. 61/947,372 (012PRV), the disclosure ofwhich is herein incorporated by reference:

-   1. A continuous process for producing a solid carbonate material    from a gaseous source of CO₂, the continuous process comprising:

a) contacting a gaseous source of CO₂ with an aqueous medium underconditions sufficient to produce a liquid condensed phase(LCP)composition;

b) introducing a cation source into the LCP composition under carbonateprecipitation conditions sufficient to produce a precipitated carbonatecomposition; and

c) dewatering the precipitated carbonate composition to produce a solidcarbonate material.

-   2. The continuous process according to Clause 1, wherein step (a)    further comprises removing hydrogen ions from the LCP composition to    produce an alkaline LCP composition.-   3. The continuous process according to Clause 2, wherein removing    hydrogen ions comprises contacting the LCP composition with an    H⁺/bicarbonate selective membrane.-   4. The continuous process according to Clauses 1, 2 or 3, wherein    step (a) further comprises removing hydrogen ions from the aqueous    medium to increase the alkalinity of the aqueous medium prior to    contacting the aqueous medium with the gaseous source of CO₂.-   5. The continuous process according to Clause 4, wherein removing    hydrogen ions comprises contacting the aqueous medium with an H⁺    selective membrane.-   6. The continuous process according to any of the preceding clauses,    wherein the method further comprises removing dissolved CO₂ from the    alkaline liquid condensed phase composition to produce a    concentrated LCP composition.-   7. The continuous process according to Clause 6, wherein removing    dissolved CO₂ comprises contacting the LCP composition with    CO₂/bicarbonate selective membrane.-   8. The continuous process according to any of the preceding clauses,    wherein the gaseous source of CO₂ is a multicomponent gaseous stream    that includes N₂.-   9. The continuous process according to Clause 8, wherein the    step (a) further comprises removing N₂ from the gaseous source of    CO₂.-   10. The continuous according to Clause 9, wherein the N₂ is removed    from the gaseous source of CO₂ by contacting the gaseous source of    CO₂ with an N₂ selective membrane.-   11. The continuous process according to any of Clauses 1 to 10,    wherein the gaseous source of CO₂ is a flue gas.-   12. The continuous process according to Clause 11, wherein the flue    gas is obtained from an industrial source.-   13. The continuous process according to any of Clauses 1 to 12,    wherein the cation source comprises an alkaline earth metal cation.-   14. The continuous process according to Clause 13, wherein the    cation source is a source of divalent cations.-   15. The continuous process according to Clause14, wherein the    divalent cations are alkaline earth metal cations.-   16. The continuous process according to Clause 15, wherein the    divalent alkaline earth metal cations are selected from the group    consisting of Ca²⁺ and Mg²⁺, and combinations thereof.-   17. The continuous process according to any of Clauses 13 to 16,    wherein the cation source is a concentrated cation source that is    produced from a hard water source.-   18. The continuous process according to Clause 17, wherein the    concentrated cation source is produced from a hard water source by    contacting the hard water source with a membrane under conditions    sufficient to produce the concentrated cation source.-   19. The continuous process according to any of the preceding    clauses, wherein the carbonate precipitation conditions are    transient amorphous calcium carbonate precipitation conditions.-   20. The continuous process according to any of the preceding    clauses, wherein the carbonate precipitation conditions produce a    first precipitated carbonate composition and second precipitated    carbonate composition.-   21. The continuous process according to Clause 20, wherein the first    precipitated carbonate composition is amorphous calcium carbonate    (ACC) and the second precipitated carbonate composition is vaterite    precursor ACC.-   22. The continuous process according to Clauses 20 and 21, wherein    the method further comprises separating the first and second    precipitated carbonate compositions from each other.-   23. The continuous process according to Clause 22, wherein the first    and second precipitated carbonate compositions are separated from    each other with a membrane.-   24. The continuous process according to any of Clauses 22 or 23,    wherein the method further comprises combining the separated first    and second precipitated carbonate compositions.-   25. The continuous process according to any of the preceding    clauses, wherein the method further comprises recovering CO₂    produced from carbonate precipitation.-   26. The continuous process according to Clause 25, wherein the    method further comprises contacting the recovered CO₂ with an    aqueous medium to produce an LCP composition.-   27. The continuous process according to any of the preceding    clauses, wherein the method further comprises introducing a setting    fluid into the precipitated carbonate composition.-   28. The continuous process according to any of the preceding    clauses, wherein dewatering comprises contacting the precipitated    carbonate composition with a membrane to produce the solid carbonate    material.-   29. The continuous process according to any of the preceding    clauses, wherein the solid carbonate material is a paste.-   30. The continuous process according to Clause 29, wherein the    method further comprises producing unit sized objects from the    paste.-   31. The continuous process according to Clause 30, wherein the    method further comprises curing the unit sized objects.-   32. The continuous process according to Clause 31, wherein curing    comprises immersing the unit sized objects in a setting solution.-   33. The continuous process according to any of the Clauses 28 to 32,    wherein the dewatering comprises extruding the precipitated    carbonate composition.-   34. The continuous process according to Clause 33, wherein the    extruding comprises applying pressure to remove liquid from the    paste.-   35. The continuous process according to Clauses 33 or 34, wherein    the extruding comprises applying negative pressure to remove air    from the paste.-   36. The continuous process according to any of the preceding    clauses, wherein the method further comprises introducing one or    more property modulators into the process so that the solid    carbonate material comprises the property modulator.-   37. The continuous process according to Clause 36, wherein the one    or more property modulators comprises a reflectance modulator, a    pigment and a biocide.-   38. The continuous process according to Clause 37, wherein the    reflectance modulator comprises a UV reflectance modulator.-   39. The continuous process according to Clause 38, wherein the UV    reflectance modulator comprises a UV absorbing pigment.-   40. The continuous process according to any of the preceding    clauses, wherein the continuous process has a process time ranging    from 5 minutes to 5 hours.-   41. A continuous reactor comprising:

a) an LCP production unit configured to contact a gaseous source of CO₂with an aqueous medium under conditions sufficient to produce a LCPcomposition;

b) a carbonate precipitation unit configured to introduce a cationsource into the LCP composition under carbonate precipitation conditionssufficient to produce a precipitated carbonate composition; and

c) a dewatering unit configured to remove water from the precipitatedcarbonate composition to produce a solid carbonate material.

-   42. The continuous reactor according to Clause 41, wherein the LCP    production unit comprises an H⁺ selective membrane.-   43. The continuous reactor according to any of Clauses 41 and 42,    wherein the LCP production unit comprises a CO₂/bicarbonate    selective membrane.-   44. The continuous reactor according to any of Clauses 41, 42 and    43, wherein the gaseous source of CO₂ is a multicomponent gaseous    stream that includes N₂ and the system further comprises an    N₂/bicarbonate selective membrane.-   45. The continuous reactor according to any of Clauses 41 to 44,    wherein the gaseous source of CO₂ is a flue gas.-   46. The continuous reactor according to Clause 45, wherein the flue    gas is obtained from an industrial source.-   47. The continuous reactor according to Clause 46, wherein the    reactor is co-located with the industrial source.-   48. The continuous reactor according to any of Clauses 41 to 47,    wherein the system comprises a membrane configured to produce the    cation source from a hard water source.-   49. The continuous reactor according to any of Clauses 41 to 48,    wherein the carbonate precipitation unit comprises a membrane    configured to separate precipitated carbonates each other.-   50. The continuous reactor according to any of Clauses 41 to 49,    wherein the system further comprises a second LCP production unit    configured to produce an LCP composition from CO₂ gas recovered from    the carbonate precipitation unit.-   51. The continuous reactor according to any of Clauses 41 to 50,    wherein dewatering unit comprises a membrane configured to produce    the solid carbonate material from the precipitated carbonate    composition.-   52. The continuous reactor according to any of Clauses 41 to 51,    wherein the solid carbonate material is a paste and the system is    configured to produce unit sized objects from the paste.-   53. The continuous reactor according to any of Clauses 41 to 52,    wherein the dewatering unit comprises an extruder.-   54. The continuous reactor according to any of Clauses 41 to 53,    wherein the continuous reactor is configured to produce the solid    carbonate composition from the source of CO₂ gas in a process time    ranging from 5 minutes to 5 hours.

Notwithstanding the appended clauses, the disclosure is also defined bythe following clauses, which clauses are further described in U.S.Provisional Application Ser. No. 62/041,568 (014PRV), the disclosure ofwhich is herein incorporated by reference:

-   1. A method of sequestering carbon dioxide (CO₂), the method    comprising:

contacting an initial hard water with a divalent cation selectivemembrane to produce a concentrated hard water comprising an increasedconcentration of divalent cations as compared to the initial hard water;and

employing the concentrated hard water in a CO₂ sequestration protocol.

-   2. The method according to Clause 1, wherein the divalent cation    selective membrane is a nanofiltration membrane.-   3. The method according to Clause 2, wherein the concentrated hard    water comprises divalent cation concentration that is 500 ppm or    greater.-   4. The method according to any one of the preceding clauses, wherein    the concentrated hard water comprises one or more divalent alkaline    earth metal cations.-   5. The method according to Clause 4, wherein the one or more    divalent alkaline earth metal cations comprise one or more of Ca²⁺    and Mg²⁺.-   6. The method according to any one of the preceding clauses, wherein    the initial hard water is obtained from a naturally occurring hard    water source.-   7. The method according to Clause 6, wherein the naturally occurring    hard water source is co-located with a location where the CO₂    sequestration protocol is conducted.-   8. The method according to any one of the preceding clauses, wherein    the initial hard water comprises a water that is produced at an oil    field.-   9. The method according to any one of the preceding clauses, wherein    the initial hard water comprises a water that is produced by a    fracking operation.-   10. The method according to any one of the preceding clauses,    wherein the initial hard water comprises an industrial waste water.-   11. The method according to any one of the preceding clauses,    wherein the CO₂ sequestration protocol is a bicarbonate-mediated CO₂    sequestration protocol.-   12. The system according to Clause 11, wherein the CO₂ sequestration    protocol comprises contacting the concentrated hard water with a    liquid condensed phase (LCP) composition.-   13. The method according to any one of the preceding clauses,    wherein the CO₂ sequestration protocol is a carbonate-mediated CO₂    sequestration protocol.-   14. The method according to any one of the preceding clauses,    wherein the method comprises combining a scaling retarding amount of    an acidic solution with the concentrated hard water.-   15. The method according to Clause 14, wherein the acidic solution    is an acidic by-product of a forward osmosis and/or alkali recovery    mediated process.-   16. A system for sequestering CO₂, the system comprising:

a hard water concentrator comprising a divalent cation selectivemembrane, wherein the hard water concentrator is configured to produce aconcentrated hard water from an initial hard water; and

a CO₂ sequestration unit configured to employ the concentrated hardwater and a source of CO₂ gas in a CO₂ sequestration protocol.

-   17. The system according to Clause 16, wherein the divalent cation    selective membrane is a nanofiltration membrane.-   18. The system according to Clause 17, wherein the concentrated hard    water has a divalent cation concentration of 500 ppm or greater.-   19. The system according to any one of Clauses 16 to 18, wherein the    concentrated hard water comprises one or more divalent alkaline    earth metal cations.-   20. The system according to Clause 19, wherein the one or more    divalent alkaline earth metal cations comprise one or more of Ca²⁺    and Mg²⁺.-   21. The system according to any one of Clauses 16 to 20, wherein the    initial hard water is a naturally occurring hard water.-   22. The system according to any one of Clauses 16 to 20, wherein the    initial hard water is a hard water produced from an oil field.-   23. The system according to any one of Clauses 16 to 20, wherein the    initial hard water is a hard water produced by a fracking operation.-   24. The system according to any one of Clauses 16 to 20, wherein the    initial hard water is a waste water.-   25. The system according to any one of Clauses 16 to 24, wherein the    hard water concentrator is in fluidic communication with a hard    water source.-   26. The system according to any one of Clauses 15 to 25, wherein the    CO₂ sequestration protocol is a bicarbonate-mediated CO₂    sequestration protocol.-   27. The system according to Clause 26, wherein the CO₂ sequestration    protocol comprises contacting the concentrated hard water with a    liquid condensed phase (LCP) composition.-   28. The system according to any one of Clauses 16 to 25, wherein the    CO₂ sequestration protocol is a carbonate-mediated CO₂ sequestration    protocol.-   29. The system according to any one of Clauses 16 to 28, wherein the    source of the CO₂ containing gas is an industrial plant.-   30. The system according to Clause 29, wherein the source of the CO₂    containing gas is a flue gas.-   31. The system according to Clause 29 or 30, wherein the industrial    plant is a power plant, cement plant or modular, gas-fired engine.-   32. The system according to any one of Clauses 16 to 31, wherein the    system is co-located with an industrial plant.

Notwithstanding the appended clauses, the disclosure is also defined bythe following clauses, which clauses are further described in U.S.Provisional Application Ser. No. 62/051,100 (015PRV), the disclosure ofwhich is herein incorporated by reference:

-   1. A method of sequestering carbon dioxide (CO₂), the method    comprising:

(a) removing hydronium ions from an aqueous medium to produce analkaline aqueous medium and an acidic by-product; and

(b) employing the alkaline aqueous medium in a CO₂ sequestrationprotocol.

-   2. The method according to Clause 1, wherein the removing comprises    positioning the aqueous medium as a feed liquid relative to a draw    liquid under conditions sufficient such that hydronium ions move    from the aqueous medium into the draw liquid.-   3. The method according to Clause 2, wherein the draw liquid    comprises a high ionic strength liquid medium.-   4. The method according to Clause 2, wherein the draw liquid    comprises a high alkalinity liquid medium.-   5. The method according to any of Clauses 2 to 4, wherein the draw    liquid comprises non-hydrogen monovalent cations to exchange with    hydronium ions in the aqueous medium.-   6. The method according to Clause 5, wherein the non-hydrogen    monovalent cations comprise one or more of: Na+ and K+.-   7. The method according to any of the preceding clauses, wherein the    aqueous medium is selected from the group consisting of a fresh    water, a waste water, a brackish water, and a seawater.-   8. The method according to any of Clauses 2 to 7, wherein the draw    liquid is selected from a geological brine and a brine discharge    from a desalination plant.-   9. The method according to any of Clauses 2 to 8, wherein a CO₂    barrier is positioned between the aqueous medium and the draw    liquid.-   10. The method according to any of Clauses 1 to 9, wherein the    method comprises combining a CO₂-containing gas with the aqueous    medium.-   11. The method according to Clause 10, wherein the method comprises    applying pressure to the aqueous medium.-   12. The method according to any of Clauses 1 to 11, wherein the    method comprises separating alkaline earth metal ions from a    precursor aqueous medium to produce the aqueous medium.-   13. The method according to Clause 12, wherein the alkaline earth    metal ions are separated from the precursor aqueous medium by    contacting the precursor aqueous medium with a divalent cation    selective membrane.-   14. The method according to 13, wherein the divalent cation    selective membrane is a nanofiltration membrane.-   15. The method according to Clause 14, wherein the alkaline earth    metal ions separated from the precursor aqueous medium comprise one    or more of Ca, Mg, Sr and Ba ions.-   16. The method according to any of the preceding clauses, wherein    removing hydronium ions comprises contacting the aqueous medium with    an H⁺ selective membrane.-   17. The method according to Clause 16, wherein the alkaline earth    metal ion depleted aqueous medium is contacted with the H⁺ selective    membrane at a contact pressure greater than 1 ATM.-   18. The method according to Clause 17, wherein the contact pressure    ranges from 4 to 50 ATM.-   19. The method according to any of the preceding clauses, wherein    the CO₂ sequestration protocol is a bicarbonate-mediated CO₂    sequestration protocol.-   20. The method according to Clause 19, wherein the CO₂ sequestration    protocol comprises contacting the alkaline aqueous medium with a    source of CO₂ gas to produce a bicarbonate composition.-   21. The method according to Clause 20, wherein the bicarbonate    composition is a liquid condensed phase (LCP) composition.-   22. The method according to Clauses 20 or 21, wherein the source of    CO₂ gas is a flue gas.-   23. The method according to Clause 22, wherein the source of CO₂ gas    is an industrial plant.-   24. The method according to any of Clauses 19 to 23, wherein the CO₂    sequestration protocol comprises contacting the bicarbonate    composition with a source of alkaline earth metal ions to produce a    precipitated carbonate composition and purified CO₂ gas.-   25. The method according to Clause 24, wherein the source of    alkaline earth metal ions comprises the alkaline earth metal ions    separated from a carbonate buffered aqueous medium.-   26. The method according to Clause 25, wherein the method further    comprises contacting the purified CO₂ gas with an aqueous medium to    produce an LCP composition.-   27. The method according to any of the preceding clauses, wherein    the method comprises returning at least a portion of the acidic    by-product to its place of origin.-   28. The method according to any of the preceding clauses, wherein    the method comprises employing at least a portion of the acidic    by-product as a feedwater for desalination.-   29. The method according to any of Clauses 1 to 18, wherein the CO₂    sequestration protocol is a carbonate-mediated CO₂ sequestration    protocol.-   30. The method according to any of the preceding clauses, wherein    the CO₂ sequestration protocol produces a building material.-   31. A system for sequestering CO₂, the system comprising:

(a) a hydronium ion remover configured to remove hydronium ions from anaqueous medium to produce an alkaline aqueous medium and an acidicby-product; and

(b) a CO₂ sequestration unit configured to employ the alkaline aqueousmedium and a source of CO₂ gas in a CO₂ sequestration protocol.

-   32. The system according to Clause 31, wherein the hydronium ion    remover comprises a draw liquid.-   33. The system according to Clause 32, wherein the draw liquid    comprises a high ionic strength medium or a high alkalinity    solution.-   34. The system according to any of Clauses 31 to 33, wherein the    hydronium ion remover comprises an H⁺ selective membrane.-   35. The system according to Clause 34, wherein the H⁺ selective    membrane is at a contact pressure greater than 1 ATM.-   36. The system according to any of Clauses 31 to 35, wherein the    system further comprises an alkaline earth metal ion separator    configured to separate alkaline earth metal ions from a precursor    aqueous medium to produce the aqueous medium.-   37. The system according to Clause 36, wherein the alkaline earth    metal ion separator comprises a divalent cation selective membrane.-   38. The system according to Clause 37, wherein the divalent cation    selective membrane is a nanofiltration membrane.-   39. The system according to any of Clauses 31 to 38, wherein the    source of CO₂ gas is an industrial plant.-   40. The system according to Clause 39, wherein the CO₂ gas is a flue    gas.-   41. The system according to any of Clauses 39 or 40, wherein the    industrial plant is a power plant, cement plant or modular,    gas-fired engine.-   42. The system according to any of Clauses 31 to 41, wherein the    system is co-located with an industrial plant.-   43. The system according to any of Clauses 31 to 42, wherein the CO₂    sequestration unit is configured to contact a bicarbonate    composition with a source of alkaline earth metal ions to produce a    precipitated carbonate composition and purified CO₂ gas.-   44. The system according to Clause 43, wherein the source of    alkaline earth metal ions comprises the alkaline earth metal ions    separated from a precursor aqueous medium in the alkaline earth    metal ion separator and the CO₂ sequestration unit is fluidically    coupled to the alkaline earth metal ion separator.-   45. The system according to any of Clauses 31 to 44, wherein the    system is configured to employ the acidic by-product as a feedwater    for desalination and the hydronium ion remover is fluidically    coupled to a desalination plant.-   46. The system according to any of Clauses 31 to 45, wherein the    hydronium ion remover is fluidically coupled to a source of a fresh    water, a brackish water, and a seawater.-   47. The system according to any of Clauses 32 to 45, wherein the    draw liquid is a geological brine or a brine discharge from a    desalination plant.-   48. The system according to any of Clauses 31 to 47, wherein the CO₂    sequestration unit is configured to produce a building material.

Notwithstanding the appended clauses, the disclosure is also defined bythe following clauses, which clauses are further described in U.S.Provisional Application Ser. No. 61/990,486 (018PRV), the disclosure ofwhich is herein incorporated by reference:

-   1. A method of producing a carbon dioxide (CO₂) capture liquid, the    method comprising:

introducing a draw liquid and a feedwater into a forward osmosisreactor, wherein the feedwater has a lower alkalinity than that of thedraw liquid; and

obtaining from the forward osmosis reactor a product draw liquid ofreduced salinity and a CO₂ capture liquid having an alkalinity that ishigher than that of the feedwater.

-   2. The method according to Clause 1, wherein the feedwater is a    seawater, brackish water, hard water or freshwater.-   3. The method according to Clauses 1 or 2, wherein the feedwater has    a lower alkalinity as compared to the draw liquid.-   4. The method according to any of Clauses 1, 2 or 3, wherein the    draw liquid is a brine.-   5. The method according to Clause 4, wherein the brine is a    geological brine, oil field produced brine water, fracking operation    produced water brine or desalination brine.-   6. The method according to any of the preceding clauses, wherein the    method further comprises contacting the CO₂ capture liquid with a    carbon dioxide (CO₂) containing gas.-   7. The method according to Clause 6, wherein the CO₂ containing gas    is a multicomponent gaseous stream.-   8. The method according to Clause 7, wherein the multicomponent    gaseous stream is a flue gas.-   9. The method according to Clause 8, wherein the flue gas is from an    industrial plant.-   10. The method according to any of the preceding clauses, wherein    the feedwater comprises dissolved inorganic carbon (DIC).-   11. The method according to Clause 10, wherein the method comprises    charging the feedwater with CO₂ before the feedwater is introduced    into the forward osmosis reactor.-   12. The method according to any of the Clauses 6 to 11, wherein the    CO₂ capture liquid is contacted with a carbon dioxide (CO₂)    containing gas in a manner sufficient to produce a liquid condensed    phase (LCP) composition.-   13. The method according to Clause 12, wherein the method comprises    contacting the LCP composition with a source of divalent cations    under carbonate precipitation conditions sufficient to produce a    carbonate precipitate.-   14. The method according to Clause 13, wherein the source of    divalent cations comprises one or more divalent alkaline earth metal    cations.-   15. The method according to Clause 14, wherein the divalent alkaline    earth metal cations comprise one or more of Ca²⁺ and Mg²⁺.-   16. The method according to any of Clauses 13 to 15, wherein the    carbonate precipitation conditions comprise bicarbonate ion mediated    carbonate precipitation conditions.-   17. The method according to Clause 16, wherein the bicarbonate ion    mediated carbonate precipitation conditions generate CO₂ gas.-   18. The method according to any of Clauses 13 to 17, wherein the    method comprises storing the LCP composition for a period of time    prior to contacting the LCP composition with a source of divalent    cations.-   19. The method according to any of Clauses 13 to 18, wherein the    method further comprises producing a solid carbonate material from    the carbonate precipitate.-   20. The method according to Clause 19, wherein the method comprises    producing a building material from the solid carbonate material.-   21. The method according to any of Clauses 1 to 20, wherein the    method comprises disposing the product draw liquid in a deep water    or subterranean location.-   22. A system for producing a carbon dioxide (CO₂) capture liquid,    the system comprising:

a forward osmosis reactor comprising a draw liquid input and a feedwaterinput;

a draw liquid source fluidically coupled to the draw liquid input of theforward osmosis reactor; and

a feedwater source fluidically coupled to the feedwater input of theforward osmosis reactor, wherein the feedwater source comprises afeedwater having a lower salinity than that of the draw liquid;

wherein the forward osmosis reactor is configured to produce a productdraw liquid of reduced salinity and a CO₂ capture liquid from thefeedwater, respectively.

-   23. The system according to Clause 22, wherein the feedwater    comprises a seawater, brackish water, hard water or freshwater.-   24. The system according to Clauses 22 or 23, wherein the system    further comprises comprises a CO₂ charging reactor configured to    contact the CO₂ capture liquid with a CO₂ containing gas.-   25. The system according to Clause 24, wherein the CO₂ containing    gas is a multicomponent gaseous stream.-   26. The system according to Clause 25, wherein the multicomponent    gaseous stream is a flue gas.-   27. The system according to Clause 26, wherein the flue gas is from    an industrial plant.-   28. The system according to Clause 27, wherein the industrial plant    is a power plant.-   29. The system according to any of Clauses 24 to 28, wherein the    system further comprises a carbonate precipitation reactor    configured to receive a product liquid from the CO₂ charging reactor    and a source of divalent cations and output a carbonate precipitate    product.-   30. The system according to any of Clauses 22 to 29, wherein the    system further comprises a storage unit configured to store a CO₂    capture liquid output from the forward osmosis reactor.

Notwithstanding the appended clauses, the disclosure is also defined bythe following clauses, which clauses are further described in U.S.Provisional Application Ser. No. 62/056,377 (020PRV), the disclosure ofwhich is herein incorporated by reference:

-   1. A method of increasing the alkalinity of a first liquid, the    method comprising: introducing the first liquid and a second liquid    into a membrane system comprising a membrane that is more permissive    of Na⁺ transport as compared to Cl⁻transport and catalyzes the    production of H⁺ and OH⁻ from H₂O to produce a product liquid from    the first liquid that has an increased alkalinity relative to the    first liquid.-   2. The method according to Clause 1, wherein the membrane system    comprises a metal particle composite membrane system.-   3. The method according to Clause 2, wherein the metal particle    composite membrane system comprises metal particles stably    associated with a membrane component, wherein the metal particles    catalyze the production of H⁺ and OH⁻ from H₂O.-   4. The method according to any of Clauses 1 to 3, wherein the pH    difference between the product liquid and the first liquid ranges    from 0.1 to 10.-   5. The method according to Clause 4, wherein the product liquid has    a pH ranging from 6 to 13.-   6. The method according to any of the preceding clauses, wherein the    first liquid is a carbon dioxide (CO₂) charged liquid.-   7. The method according to Clause 6, wherein the CO₂ charged liquid    is a CO₂ charged seawater, brackish water, hard water or freshwater.-   8. The method according to any of the preceding clauses, wherein the    second liquid is a brine.-   9. The method according to Clause 8, wherein the brine draw liquid    is a geological brine, oil field produced brine water, fracking    operation produced water brine or desalination brine.-   10. The method according to any of the preceding clauses, wherein    the membrane mediates ion transport by dehydration/resolvation.-   11. The method according to Clause 10, wherein the membrane is a    cellulose acetate membrane.-   12. The method according to Clause 10, wherein the membrane is a    polyvinyl alcohol membrane.-   13. The method according to any of Clauses 3 to 12, wherein the    metal particles have a diameter ranging from 1 to 10,000 nm.-   14. The method according to Clause 13, wherein the metal particles    comprise a metal selected from the group consisting of nickel and    zinc.-   15. The method according to any of Clauses 6 to 14, wherein the    method further comprises producing the CO₂ charged liquid by    contacting an initial liquid or the product liquid with a carbon    dioxide (CO₂) containing gas.-   16. The method according to Clause 15, wherein the CO₂ containing    gas is a multicomponent gaseous stream.-   17. The method according to Clause 16, wherein the multicomponent    gaseous stream is a flue gas.-   18. The method according to Clause 17, wherein the flue gas is from    an industrial plant.-   19. The method according to any of the preceding clauses, wherein    the product liquid is a bicarbonate containing liquid.-   20. The method according to any of the preceding clauses, wherein    the method comprises producing an LCP containing liquid from the    product liquid.-   21. The method according to Clause 20, wherein the method comprises    contacting the LCP containing liquid with a source of divalent    cations under carbonate precipitation conditions sufficient to    produce a carbonate precipitate.-   22. The method according to Clause 21, wherein the source of    divalent cations comprises one or more divalent alkaline earth metal    cations.-   23. The method according to Clause 22, wherein the divalent alkaline    earth metal cations comprise one or more of Ca²⁺ and Mg²⁺.-   24. The method according to any of Clauses 21 to 23, wherein the    carbonate precipitation conditions comprise bicarbonate ion mediated    carbonate precipitation conditions.-   25. The method according to Clause 24, wherein the bicarbonate ion    mediated carbonate precipitation conditions generate CO₂ gas.-   26. The method according to any of Clauses 21 to 25, wherein the    method further comprises producing a solid carbonate material from    the carbonate precipitate.-   27. The method according to Clause 26, wherein the method comprises    producing a building material from the solid carbonate material.-   28. A system for increasing the alkalinity of a first liquid, the    system comprising:

a membrane system having a first liquid input, second liquid input andproduct liquid output, wherein the membrane system is more permissive ofNa⁺ transport as compared to Cl⁻ transport and catalyzes the productionof H⁺ and OH⁻ from H₂O;

a first liquid fluidically coupled to the first liquid input; and

a second liquid fluidically coupled to the second liquid input.

-   29. The system according to Clause 28, wherein the membrane system    comprises a metal particle composite membrane system.-   30. The system according to Clause 29, wherein the metal particle    composite membrane system comprises metal particles stably    associated with a membrane component, wherein the metal particles    catalyze the production of H⁺ and Oft from H₂O.-   31. The system according to any of Clauses 28 and 30, wherein the    system further comprises a reactor configured to contact an a liquid    with a CO₂ containing gas, wherein the liquid is at least one of the    first liquid and product liquid.-   32. The system according to Clause 31, wherein the CO₂ containing    gas is a multicomponent gaseous stream.-   33. The system according to Clause 32, wherein the multicomponent    gaseous stream is a flue gas.-   34. The system according to Clause 33, wherein the flue gas is from    an industrial plant.-   35. The system according to Clause 34, wherein the industrial plant    is a power plant.

36. The system according to any of Clauses 28 to 35, wherein the secondliquid is a brine.

-   37. The system according to Clause 36, wherein the brine is a    geological brine, oil field produced brine water, fracking operation    produced water brine or desalination brine.-   38. The system according to any of Clauses 28 to 37, wherein the    membrane system mediates ion transport by dehydration/resolvation.-   39. The system according to Clause 38, wherein the membrane system    comprises a cellulose acetate membrane.-   40. The system according to Clause 38, wherein the membrane system    comprises is a polyvinyl alcohol membrane.-   41. The system according to any of Clauses 30 to 40, wherein the    metal particles have a diameter ranging from 1 to 10,000 nm.-   42. The system according to Clause 41, wherein the metal particles    comprise a metal selected from the group consisting of nickel and    zinc.-   43. The system according to any of Clauses 28 to 42, wherein the    system further comprises a carbonate precipitation reactor    configured to receive a bicarbonate containing liquid and a source    of divalent cations and output a carbonate precipitate product.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is readily apparent to those of ordinary skill in theart in light of the teachings of this invention that certain changes andmodifications may be made thereto without departing from the spirit orscope of the appended claims.

Accordingly, the preceding merely illustrates the principles of theinvention. It will be appreciated that those skilled in the art will beable to devise various arrangements which, although not explicitlydescribed or shown herein, embody the principles of the invention andare included within its spirit and scope. Furthermore, all examples andconditional language recited herein are principally intended to aid thereader in understanding the principles of the invention and the conceptscontributed by the inventors to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments of the invention as well asspecific examples thereof, are intended to encompass both structural andfunctional equivalents thereof.

Additionally, it is intended that such equivalents include bothcurrently known equivalents and equivalents developed in the future,i.e., any elements developed that perform the same function, regardlessof structure. The scope of the present invention, therefore, is notintended to be limited to the exemplary embodiments shown and describedherein. Rather, the scope and spirit of present invention is embodied bythe appended claims.

1 to
 80. (canceled)
 81. A system for sequestering CO₂ from a gaseoussource of CO₂, the system comprising: an alkali enrichment module; a CO₂gas/liquid contactor module; and a carbonate production module.
 82. Thesystem according to claim 81, wherein the alkali enrichment module is amembrane mediated alkali enrichment module.
 83. The system according toclaim 81, wherein the CO₂ gas/liquid contactor module comprises a hollowfiber membrane.
 84. The system according to claim 81, wherein thecarbonate production module is configured to produce a carbonate slurry.85. The system according to claim 81, wherein the carbonate productionmodule is configured to produce a non-slurry carbonate solid.
 86. Thesystem according to claim 81, wherein the system is operatively coupledto sources of first and second distinct liquids.
 87. The systemaccording to claim 81, wherein the system is operatively coupled to agaseous source of CO_(2.)
 88. The system according to claim 81, whereinthe gaseous source of CO₂ is a multi-component gaseous stream.
 89. Thesystem according to claim 88, wherein the gaseous source of CO₂ is aflue gas.
 90. The system according to claim 81, wherein at least two ofthe: an alkali enrichment module; a CO₂ gas/liquid contactor module; anda carbonate production module are configured to operate at the sameoperating pressure.
 91. The system according to claim 81, wherein all ofthe: an alkali enrichment module; a CO₂ gas/liquid contactor module; anda carbonate production module are configured to operate at the sameoperating pressure.
 92. The system according to claim 90, wherein theoperating pressure ranges from 1 to 10 ATM.
 93. The system according toclaim 81, wherein the system is configured to recycle a gas or liquidamong at least two of the: an alkali enrichment module; a CO₂ gas/liquidcontactor module; and a carbonate production module.
 94. The systemaccording to claim 81, wherein the system is configured to processindustrial scale volumes of input gasses and liquids.